msm-camera: Added the  NULL check in gemini driver.

Adding NULL check for ionhandle and y_off in gemini driver files.

CRs-Fixed: 504159

Change-Id: I6d20298183bec0c3c2c16088a936ac6f7d307da4
Signed-off-by: Katta Santhisindhu <kattas@codeaurora.org>