[media] s5p-fimc: fimc-lite: Remove empty s_power subdev callback

The .s_power FIMC-LITE subdev callback is now empty and
unneeded. The FIMC-LITE IP power handling will be done
by the FIMC-IS driver, so just remove the callback.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>