pan/bi: Allow non-terminal BLEND operations

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <!8417>
41 jobs for !8417 with bifrost-mrt in 10 minutes and 52 seconds (queued for 4 seconds)
merge request