media: verisilicon: HEVC: Initialize start_bit field

The HEVC driver needs to set the start_bit field explicitly to avoid
causing corrupted frames when the VP9 decoder is used in parallel. The
reason for this problem is that the VP9 and the HEVC decoder share this
register.

Fixes: cb5dd5a0 ("media: hantro: Introduce G2/HEVC decoder")
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Tested-by: Nicolas Dufresne <nicolas.dufresne@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@xs4all.nl>