x86/mpx/selftests: Adjust the self-test to fresh distros that export the MPX ABI

x86/mpx/selftests: Adjust the self-test to fresh distros that export the MPX ABI

Fix this warning:

  mpx-mini-test.c:422:0: warning: "SEGV_BNDERR" redefined

Cc: 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>
Cc: akpm@linux-foundation.org
Cc: dave.hansen@intel.com
Cc: linux-mm@kvack.org
Cc: linuxram@us.ibm.com
Cc: mpe@ellerman.id.au
Cc: shakeelb@google.com
Cc: shuah@kernel.org
Link: http://lkml.kernel.org/r/20180514085908.GA12798@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>