msm: camera: isp: fix an issue in scratch buffer configuration

When configure the scratch buffer, wrong pingpong bit location is
programmed. So the VFE hardware can still write to the same buffer
which has been diverted to other camera compoment. This cause the image
corruption.

Change-Id: I6d5cfe0c00a237efb3ab3dff87459341736d45a7
Signed-off-by: Jing Zhou <jzhou70@codeaurora.org>