x86/kbuild: Eliminate duplicate command line options

The options -mno-mmx and -mno-sse are unconditionally added to
KBUILD_CFLAGS in both branches of an ifeq and through a
$(cc-option) further down. We can safely remove the first
instances.

In fact, since the -mno-mmx and -mno-sse options were introduced
simultaneous with the other two options in the $(cc-option)
[according to http://www.gnu.org/software/gcc/gcc-3.1/changes.html],
and since the former were unconditionally used, one can deduce that
only gcc versions knowing about all four are supported. So also
eliminate the $(cc-option) wrap.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Peter Foley <pefoley2@pefoley.com>
Link: http://lkml.kernel.org/r/1410365139-24440-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Ingo Molnar <mingo@kernel.org>