media: rkvdec: Add variants support

media: rkvdec: Add variants support

Different versions of the Rockchip VDEC IP exists and one way they can
differ is what decoding formats are supported.

Add a variant implementation in order to support flagging different
capabilities.

Signed-off-by: Alex Bee <knaerzche@gmail.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Diederik de Haas <didi.debian@cknow.org>  # Rock64, RockPro64, Quartz64-B, NanoPi R5S
Tested-by: Detlev Casanova <detlev.casanova@collabora.com> # RK3399
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>