x86, MCE, AMD: Move invariant code out from loop body

Assigning to mce_threshold_vector is loop-invariant code in
mce_amd_feature_init(). So do it only once, out of loop body.

Signed-off-by: Chen Yucong <slaoub@gmail.com>
Link: http://lkml.kernel.org/r/1412263212.8085.6.camel@debian


[ Boris: commit message corrections. ]
Signed-off-by: Borislav Petkov <bp@suse.de>