x86: Fix resume from suspend when CONFIG_CC_STACKPROTECTOR

Patch 08687aec71bc9134fe336e561f6did877bacf74fc0a (x86: unify
power/cpu_(32|64).c)  renamed cpu_32.c to cpu.c, but did not update
the special compilation flags for the file for the new name.

This patch fixes the compilation flags, and therefore fixes resume
from suspend on my Acer Aspire One.

[rjw: The regression from 2.6.30 fixed by this patch is tracked as
 http://bugzilla.kernel.org/show_bug.cgi?id=13661]

Signed-off-by: Peter Chubb <peterc@nicta.com.au>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>