msm:camera: Increase the v4l2 event queue length

Observed missing of v4l2 events to userspace media controller,
this can happen if media controller is blocked in post processing
the frames. Hence increasing the queue length gives enough time
to accomodate all the events without being overwritten with
newer events.

Change-Id: Ic3b5fd29df8c6384e83312b9c9ffd788bdf60951
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>