msm: camera: fix warnings in camera driver.

Fix the warnings seen with couple of kernel
debug flags turned on.
(CONFIG_SLUB_DEBUG_ON, CONFIG_DEBUG_MUTEXES)
The memory type used should be GFP_ATOMIC at
couple of places, since those functions are
invoked in interrupt context.
In msm_open, the mutex vid_lock was unlocked
twice. Remove the duplicate unlock.

Change-Id: Ief810f863e8ed7a60613a5f4b367b0aa799d4fb0
Signed-off-by: Kiran Kumar H N <hurlisal@codeaurora.org>