msm: camera: Validate size param before allocating memory

When ever i2c write is initiated check size param for NULL
and in case of sequence write check for maximun allowed
size per i2c sequence write.

Change-Id: I111282537663d6b263a3686927c85b8f71560dae
Changa-Id: I590c7b3d154fc7626e54d5d52f7fea7f7bc2079a
Signed-off-by: Deepak Kaushal <dkaushal@codeaurora.org>
Signed-off-by: Viswanadha Raju Thotakura <viswanad@codeaurora.org>