msm: camera: Return from DQBUF ioctl in case of error.

Incase the vb2_dqbuf call returns error, we are continuing
ahead and trying to access the fields of the vb2 buffer which
may not be initialized yet. Avoid this by checking the
return value of vb2_dqbuf and return immediately in case of
errors.

Change-Id: I33036fe9b3bd7ce2b28e9cd6e4cd5f293425be95
CRs-Fixed: 495635
Signed-off-by: Kiran Kumar H N <hurlisal@codeaurora.org>