x86, cpu, amd: Deprecate AMD-specific MSR variants

Now that all users of {rd,wr}msr_amd_safe have been fixed, deprecate its
use by making them private to amd.c and adding warnings when used on
anything else beside K8.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1338562358-28182-5-git-send-email-bp@amd64.org
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>