avtimer: Update avtimer driver to support Qdsp6v2

AVtimer in Qdsp6 provides the timer ticks for synchronization
of audio and video streams for capture and playback use cases.
Qdsp6 AVtimer interface has been updated for v2 version.
Update avtimer driver to support Qdsp6v2.

Change-Id: Ia68b04421edf13a96685654761bb71b866a5327b
Signed-off-by: Kuirong Wang <kuirongw@codeaurora.org>