media: mtk-vcodec: MT8173 h264/vp8 encoder min/max bitrate settings

Set recommend min/max bitrate range for MT8173 h264/vp8 encoder.

Signed-off-by: Irui Wang <irui.wang@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>