x86, mce: Cleanup mce_create()/remove_device()

Use temporary local variable sysdev 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/4DEED777.7080205@jp.fujitsu.com


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