greybus: camera: Use pointer for gb camera module ops

No need to duplicate module ops on every registration.

NOTE: Change should be along merged with:
"msm: camera: Change gb_camera_module ops to pointer"

Signed-off-by: Gjorgji Rosikopulos <grosikopulos@mm-sol.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>