sparc64: Stop performance counter before updating

sparc64: Stop performance counter before updating

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: 22876587

Signed-off-by: Dave Aldridge <david.j.aldridge@oracle.com>
(cherry picked from commit 6de93dc001ed2f440ed3881722934fbda2de0d4f)
(cherry picked from commit b36dd4d8040cd53f7e8de5a1d145be483d185105)
Signed-off-by: Allen Pais <allen.pais@oracle.com>