uml: remove xmm checking on x86

This patch removes some code which ran at every boot, but does not seem to do
anything anymore.  Please test.  It works for me but mistakes can happen.

Signed-off-by: Karol Swietlicki <magotari@gmail.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>