x86: extend some of Intel's recent MCE work to also support AMD

x86: extend some of Intel's recent MCE work to also support AMD

At least the MSR handling for guests can easily be made shared between
the two vendors; likely a lot of the other code in mce_intel.c could
also be made common. The goal here, however, is to eliminate the
annoying guest-tried-to-modify-msr messages that result from enabling
the MCE code on the Linux side.

Additionally (in order for not having to make the same change twice to
basically identical code) the patch also merges
amd_{fam10,k8}_mcheck_init(), enables the former to also be used for
Fam11 (I'd suppose that Fam12 would also need to go here, but I have
no data to confirm that), and does some minor (mostly coding style for
the code moved around) adjustments.

Signed-off-by: Jan Beulich <jbeulich@novell.com>