powerpc/64s: Data driven machine check handling

Move the handling (corrective action) of machine checks to the table
based evaluation.

This changes P7 and P8 ERAT flushing from using SLB flush to using ERAT
flush.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>