media: rockchip/vpu: Provide a helper to reset both src and dst formats

When initializing a context, the core wants to reset both src and dst
formats. Right now the order doesn't matter, but if we want to have a
valid default width/height on the non-coded/raw format side (src in
case of encoders, dst in case of decoders), we need to reset those
formats in the right order: first the coded-format side, then the other,
such that width and height on the raw format side can be taken from
the coded format.

Let's provide a helper that will reset both formats and make sure this
is done in the right order.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>