media: mediatek: vcodec: Fix h264 set lat buffer error

Will set lat buffer to lat_list two times when lat decode timeout for
inner racing mode.

If core thread can't get frame buffer, need to return error value.

Fixes: 59fba9ee ("media: mediatek: vcodec: support stateless H.264 decoding for mt8192")
Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>