media: verisilicon: Fix auxiliary buffer allocation size

Use v4l2_av1_tile_info->tile_cols to get the number of columns
in the frame and make auxiliary buffer memory size computation
more accurate.

Fixes: 727a4006 ("media: verisilicon: Add Rockchip AV1 decoder")
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>