media: rcar-vin: Remove unneeded calls to pm_runtime_{enable, disable}

Runtime PM is already enabled unconditionally when the driver is probed
and disabled when it's removed. There is no point in doing it again for
Gen2 when opening and closing the video device.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>