x86, cpuid: Remove the bkl from cpuid_open()

Most of the variables are local to the function. It IS possible that
for struct cpuinfo_x86 *c c could point to the same area. However,
this is used read only.

Signed-off-by: John Kacur <jkacur@redhat.com>
LKML-Reference: <alpine.LFD.2.00.0910072016190.15183@localhost.localdomain>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>