media: rkvdec: h264: Use bytesperline and buffer height as virstride

Use bytesperline and buffer height to calculate the strides configured.

This does not really change anything other than ensuring the
bytesperline that is signaled to userspace matches what is configured
in HW.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Christopher Obbard <chris.obbard@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>