x86/mpx: Re-add MPX to selftests Makefile

x86/mpx: Re-add MPX to selftests Makefile

BugLink: http://bugs.launchpad.net/bugs/1691369
commit e64d5fbe56259c94df504af8ce804cfc6a022adb upstream.

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: 5f23f6d082a9 ("x86/pkeys: Add self-tests")
Link: http://lkml.kernel.org/r/20170201225629.C3070852@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>