media: dt-bindings: media: rockchip-vdec: Add RK3328 compatible

Document the RK3328 compatible for rockchip-vdec. The driver shares
the same base functionality as the RK3399 hardware so make sure that
the RK3399 compatible is also included in the device tree.

Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>