msm: camera: common: Add validation check for cpu buffers before accessing

Add validation check before accessing the packets and configs from
the buffers.

CRs-Fixed: 2360223, 2416463
Change-Id: I9a09bc7064fd7e7914f91576542181c301db926d
Signed-off-by: Abhilash Kumar <krabhi@codeaurora.org>
Signed-off-by: Mukund Madhusudan Atre <matre@codeaurora.org>