x86, mce: Cleanup mce_read()

Use a temporary local variable m to simplify the code. No change in
logic.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/4DEED7A8.8020307@jp.fujitsu.com


Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>