msm: camera: Do not use struct v4l2_event for private ioctl

struct v4l2_event should not be used for communication via
private ioctl because v4l2_event type is meant only for communication
through the V4L2 framework. Using this outside the framework for
custom ioctls will result in improper handling when 32/64 conversion
are needed.

So change the private ioctl handler in msm.c to not use this struct.
Also update the ioctl codes to use msm_v4l2_event_data instead of
v4l2_event.

Change-Id: I556de94de8676e4c1eb217f25c77a22a62465ee5
Signed-off-by: Seemanta Dutta <seemanta@codeaurora.org>