media: platform: Improve power on and power off flow

Call pm_runtime_get_sync() before starting a frame and then
pm_runtime_put() after completing it. This can save power for the time
between processing two frames.

Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Xia Jiang <xia.jiang@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>