sparc64: Stop performance counter before updating

sparc64: Stop performance counter before updating

This commit takes the fix as implemented in commit
b36dd4d8040c and applies it to M8 devices. Original commit
message:

In order to reliably clear the PCRx.ov bit when updating a
performance counter value, we need to stop it counting first.
If we do not do this, then we can miss performance counter
overflow events.

Orabug: 25441707

Signed-off-by: Dave Aldridge <david.j.aldridge@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>