media: hantro: h264: Fix the frame_num wraparound case

Step '8.2.4.1 Decoding process for picture numbers' was missing in the
reflist creation logic, leading to invalid P reflists when a
->frame_num wraparound happens.

Fixes: a9471e25 ("media: hantro: Add core bits to support H264 decoding")
Reported-by: Francois Buergisser <fbuergisser@google.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Francois Buergisser <fbuergisser@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>