msm: vidc: handle release ref events for dynamic buffers

For dynamic output buffers, firmware can hold on to a
output buffer reference after releasing it to
driver. The buffer is marked as read only and sent
back to client. The driver maintains the reference
of this buffer and decrements it when firmware
sends the release reference event. The client is
notified of the release reference event.

Change-Id: Ie3c014af255e09f6dac9b3b853c9994b97d830b6
Signed-off-by: Arun Menon <avmenon@codeaurora.org>