EDAC/mce_amd: Print !SMCA processor warning only once

This warning is output for every virtual CPU in a guest on an EPYC 2
system because kvm doesn't enable SMCA. Once is enough too.

 [ bp: Massage. ]

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200217134627.19765-1-prarit@redhat.com