udlfb: delete the unused parameter for dlfb_handle_damage

Remove the unused parameter "data" and unused variable "ret".

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Bernie Thompson <bernie@plugable.com>
Cc: Ladislav Michl <ladis@linux-mips.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>