x86/mce: Convert static array of pointers to per-cpu variables

When I previously fixed up the mce_device code, I used a static array of
the pointers.  It was (rightfully) pointed out to me that I should be
using the per_cpu code instead.

This patch converts the code over to that structure, moving the variable
back into the per_cpu area, like it used to be for 3.2 and earlier.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Link: https://lkml.org/lkml/2012/1/27/165
Signed-off-by: Tony Luck <tony.luck@intel.com>