[PATCH] ppc64: fix oprofile sample bit handling

Oprofile was hardwiring the MMCRA sample bit to 1 but on newer cpus
(eg POWER5) we want to vary it based on the group being sampled.

Add a temporary workaround until people update their oprofile userspace.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>