msm: ipa: notify uC before going to clock gating

Before APPS is voting for IPA clocks to be disabled,
it first needs to make sure IPA uC is idle.

After APPS is voting for IPA clocks to be enabled,
uC is notified to start processing.

Change-Id: Ied9374a12d1ca2a1afe0c1aa30e6150089064101
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Ravit Katzav <rkatzav@codeaurora.org>