media: hantro: Support RK3399 VP8 decoding

Rockchip RK3399 SoC has the same Hantro G1 IP block
as RK3288, but the registers are entirely different.

In a similar fashion as MPEG-2 decoding, it's simpler
to just add a separate implementation.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>