x86, mce, severity: Make formatting a bit more readable

The table looks very complicated and hard to read for people other than
skilled developers. So let's clean it up a bit. At first, change format
to ease reading elements in the table.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/4DEED5EB.6050400@jp.fujitsu.com
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>