powerpc/64s: consolidate MCE counter increment.

The code in machine_check_exception excludes 64s hvmode when
incrementing the MCE counter only to call opal_machine_check to
increment it specifically for this case.

Remove the exclusion and special case.

Fixes: a43c1590 ("powerpc/pseries: Flush SLB contents on SLB MCE
		errors.")

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>