media: mtk-vcodec: abstract firmware interface

MT8183's codec firmware is run by a different remote processor from
MT8173. While the firmware interface is basically the same, the way to
invoke it differs. Abstract all firmware calls under a layer that will
allow us to handle both firmware types transparently.

[acourbot: refactor, cleanup and split]
[pihsun: fix error path and add mtk_vcodec_fw_release]
[hverkuil: fixed some checkpatch alignment warnings]
[hverkuil: fixed merge conflicts]

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Co-developed-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Tiffany Lin <tiffany.lin@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>