msm: ipa: add TAG process

Before gating IPA clocks there is a need to make sure that there
are no packets inside IPA HW.
A TAG process is sent to IPA HW, and when it is sent back
it is safe to gate IPA clocks.
On pipe disconnection there is a need to make sure that there
are no open aggregation frames on this pipe. A TAG process is used in
this case also.

Change-Id: I514e9b644ab1c15035f1d2fbb6087500c3f9ad6a
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Ravit Katzav <rkatzav@codeaurora.org>