msm: camera: cci: Modify condition check to read CCI data

If the buffer level is zero, we continue to wait for the
next irq and not proceed to read the data registers as part
of cci read sequence.

Change-Id: I60a9a2388789a17e5ff01742b7e8928a71cbe421
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>