msm: camera: provide NULL pointer error checks.

At certain places in the camera driver, the returned pointer
from function calls is directly being de-referenced
without NULL value checks. This change provides such
checks and appropriately handles failures.

Change-Id: I333e35df5903355336279483bc326d8f3b99de4f
Signed-off-by: Ankit Premrajka <ankitp@codeaurora.org>