[PATCH] i386: Remove unused kernel config option X86_XADD

Remove the unused kernel config option X86_XADD, which is unused in any
source or header file.

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>