x86/mpx: Re-add MPX to selftests Makefile

Ingo pointed out that the MPX tests were no longer in the selftests
Makefile.  It appears that I shot myself in the foot on this one
and accidentally removed them when I added the pkeys tests, probably
from bungling a merge conflict.
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 5f23f6d0 ("x86/pkeys: Add self-tests")
Link: http://lkml.kernel.org/r/20170201225629.C3070852@viggo.jf.intel.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/testing/selftests/x86/Makefile

@@ -5,7 +5,7 @@ include ../lib.mk
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
 TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
-			check_initial_reg_state sigreturn ldt_gdt iopl \
+			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test \
 			protection_keys test_vdso
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \