media: hantro: h264: Get the correct fallback reference buffer

media: hantro: h264: Get the correct fallback reference buffer

[ Upstream commit 6d9e8cd0553bb03e8ab9d4d2d7d17f3fb639bd86 ]

If the bitstream and the application are incorrectly configuring
the reference pictures, the hardware will need to fallback
to using some other reference picture.

When the post-processor is enabled, the fallback buffer
should be a shadow buffer (postproc.dec_q), and not a
CAPTURE queue buffer, since the latter is post-processed
and not really the output of the decoder core.

Fixes: 8c2d66b036c77 ("media: hantro: Support color conversion via post-processing")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>