arm64: KVM: hyp: debug-sr: Mark expected switch fall-through

When fall-through warnings was enabled by default the following warnings
was starting to show up:

../arch/arm64/kvm/hyp/debug-sr.c: In function ‘__debug_save_state’:
../arch/arm64/kvm/hyp/debug-sr.c:20:19: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
  case 15: ptr[15] = read_debug(reg, 15);   \
../arch/arm64/kvm/hyp/debug-sr.c:113:2: note: in expansion of macro ‘save_debug’
  save_debug(dbg->dbg_bcr, dbgbcr, brps);
  ^~~~~~~~~~
../arch/arm64/kvm/hyp/debug-sr.c:21:2: note: here
  case 14: ptr[14] = read_debug(reg, 14);   \
  ^~~~
../arch/arm64/kvm/hyp/debug-sr.c:113:2: note: in expansion of macro ‘save_debug’
  save_debug(dbg->dbg_bcr, dbgbcr, brps);
  ^~~~~~~~~~
../arch/arm64/kvm/hyp/debug-sr.c:21:19: warning: this statement may fall
 through [-Wimplicit-fallthrough=]
  case 14: ptr[14] = read_debug(reg, 14);   \
../arch/arm64/kvm/hyp/debug-sr.c:113:2: note: in expansion of macro ‘save_debug’
  save_debug(dbg->dbg_bcr, dbgbcr, brps);
  ^~~~~~~~~~
../arch/arm64/kvm/hyp/debug-sr.c:22:2: note: here
  case 13: ptr[13] = read_debug(reg, 13);   \
  ^~~~
../arch/arm64/kvm/hyp/debug-sr.c:113:2: note: in expansion of macro ‘save_debug’
  save_debug(dbg->dbg_bcr, dbgbcr, brps);
  ^~~~~~~~~~

Rework to add a 'Fall through' comment where the compiler warned
about fall-through, hence silencing the warning.

Fixes: d93512ef0f0e ("Makefile: Globally enable fall-through warning")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
[maz: fixed commit message]
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/hyp/debug-sr.c

@@ -18,40 +18,70 @@
 #define save_debug(ptr,reg,nr)						\
 	switch (nr) {							\
 	case 15:	ptr[15] = read_debug(reg, 15);			\
+			/* Fall through */				\
 	case 14:	ptr[14] = read_debug(reg, 14);			\
+			/* Fall through */				\
 	case 13:	ptr[13] = read_debug(reg, 13);			\
+			/* Fall through */				\
 	case 12:	ptr[12] = read_debug(reg, 12);			\
+			/* Fall through */				\
 	case 11:	ptr[11] = read_debug(reg, 11);			\
+			/* Fall through */				\
 	case 10:	ptr[10] = read_debug(reg, 10);			\
+			/* Fall through */				\
 	case 9:		ptr[9] = read_debug(reg, 9);			\
+			/* Fall through */				\
 	case 8:		ptr[8] = read_debug(reg, 8);			\
+			/* Fall through */				\
 	case 7:		ptr[7] = read_debug(reg, 7);			\
+			/* Fall through */				\
 	case 6:		ptr[6] = read_debug(reg, 6);			\
+			/* Fall through */				\
 	case 5:		ptr[5] = read_debug(reg, 5);			\
+			/* Fall through */				\
 	case 4:		ptr[4] = read_debug(reg, 4);			\
+			/* Fall through */				\
 	case 3:		ptr[3] = read_debug(reg, 3);			\
+			/* Fall through */				\
 	case 2:		ptr[2] = read_debug(reg, 2);			\
+			/* Fall through */				\
 	case 1:		ptr[1] = read_debug(reg, 1);			\
+			/* Fall through */				\
 	default:	ptr[0] = read_debug(reg, 0);			\
 	}
 
 #define restore_debug(ptr,reg,nr)					\
 	switch (nr) {							\
 	case 15:	write_debug(ptr[15], reg, 15);			\
+			/* Fall through */				\
 	case 14:	write_debug(ptr[14], reg, 14);			\
+			/* Fall through */				\
 	case 13:	write_debug(ptr[13], reg, 13);			\
+			/* Fall through */				\
 	case 12:	write_debug(ptr[12], reg, 12);			\
+			/* Fall through */				\
 	case 11:	write_debug(ptr[11], reg, 11);			\
+			/* Fall through */				\
 	case 10:	write_debug(ptr[10], reg, 10);			\
+			/* Fall through */				\
 	case 9:		write_debug(ptr[9], reg, 9);			\
+			/* Fall through */				\
 	case 8:		write_debug(ptr[8], reg, 8);			\
+			/* Fall through */				\
 	case 7:		write_debug(ptr[7], reg, 7);			\
+			/* Fall through */				\
 	case 6:		write_debug(ptr[6], reg, 6);			\
+			/* Fall through */				\
 	case 5:		write_debug(ptr[5], reg, 5);			\
+			/* Fall through */				\
 	case 4:		write_debug(ptr[4], reg, 4);			\
+			/* Fall through */				\
 	case 3:		write_debug(ptr[3], reg, 3);			\
+			/* Fall through */				\
 	case 2:		write_debug(ptr[2], reg, 2);			\
+			/* Fall through */				\
 	case 1:		write_debug(ptr[1], reg, 1);			\
+			/* Fall through */				\
 	default:	write_debug(ptr[0], reg, 0);			\
 	}