media: cedrus: Implement runtime PM

This allows the VE clocks and PLL_VE to be disabled most of the time.
A runtime PM reference is held while streaming.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>