msm: camera: cci: Fix burst read sequence

This change clears the threshold irq after draining the FIFO
buffer as oppose to immediately clearing it. Also added separate
complete events for threshold and read done.

Change-Id: I29f21545bb52a3c08ec1afffdd7d3f610a3055dc
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>