media: hantro: Support VP9 on the G2 core

VeriSilicon Hantro G2 core supports VP9 codec.

[hverkuil: add kerneldoc line for HANTRO_MODE_VP9_DEC]

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>