msm: camera: jpeg: Fix for race condition during flush

Add mutex lock to avoid race condition and deregister irq
call back during flush.

Change-Id: I6172a652bfa91aa45fe4c76e8bed54dab80f86d3
Signed-off-by: Vishalsingh Hajeri <vhajeri@codeaurora.org>
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>