Mark switch cases where we are expecting to fall through.

This patch fixes the following warning (Building: mips):

arch/mips/oprofile/op_model_mipsxx.c: In function ‘mipsxx_cpu_stop’:
arch/mips/oprofile/op_model_mipsxx.c:217:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl3(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:218:2: note: here
  case 3:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:219:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl2(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:220:2: note: here
  case 2:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:221:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl1(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:222:2: note: here
  case 1:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c: In function ‘mipsxx_cpu_start’:
arch/mips/oprofile/op_model_mipsxx.c:197:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl3(WHAT | reg.control[3]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:198:2: note: here
  case 3:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:199:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl2(WHAT | reg.control[2]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:200:2: note: here
  case 2:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:201:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfctrl1(WHAT | reg.control[1]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:202:2: note: here
  case 1:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c: In function ‘reset_counters’:
arch/mips/oprofile/op_model_mipsxx.c:299:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr3(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:300:2: note: here
  case 3:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:302:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr2(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:303:2: note: here
  case 2:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:305:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr1(0);
   ^~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:306:2: note: here
  case 1:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c: In function ‘mipsxx_perfcount_handler’:
arch/mips/oprofile/op_model_mipsxx.c:242:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if ((control & MIPS_PERFCTRL_IE) &&   \
      ^
arch/mips/oprofile/op_model_mipsxx.c:248:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(3)
  ^~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:239:2: note: here
  case n + 1:       \
  ^
arch/mips/oprofile/op_model_mipsxx.c:249:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(2)
  ^~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:242:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if ((control & MIPS_PERFCTRL_IE) &&   \
      ^
arch/mips/oprofile/op_model_mipsxx.c:249:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(2)
  ^~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:239:2: note: here
  case n + 1:       \
  ^
arch/mips/oprofile/op_model_mipsxx.c:250:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(1)
  ^~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:242:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if ((control & MIPS_PERFCTRL_IE) &&   \
      ^
arch/mips/oprofile/op_model_mipsxx.c:250:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(1)
  ^~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:239:2: note: here
  case n + 1:       \
  ^
arch/mips/oprofile/op_model_mipsxx.c:251:2: note: in expansion of macro ‘HANDLE_COUNTER’
  HANDLE_COUNTER(0)
  ^~~~~~~~~~~~~~
  CC      usr/include/linux/pmu.h.s
arch/mips/oprofile/op_model_mipsxx.c: In function ‘mipsxx_cpu_setup’:
arch/mips/oprofile/op_model_mipsxx.c:174:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr3(reg.counter[3]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:175:2: note: here
  case 3:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:177:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr2(reg.counter[2]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:178:2: note: here
  case 2:
  ^~~~
arch/mips/oprofile/op_model_mipsxx.c:180:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
   w_c0_perfcntr1(reg.counter[1]);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/mips/oprofile/op_model_mipsxx.c:181:2: note: here
  case 1:
  ^~~~
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Robert Richter <rric@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: oprofile-list@lists.sf.net
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>