panfrost: Allow testing if a specific batch is targeting a scanout FB

panfrost: Allow testing if a specific batch is targeting a scanout FB

Rename panfrost_is_scanout() into panfrost_batch_is_scanout(), pass it
a batch instead of a context and move the code to pan_job.c.

With this in place, we can now test if a batch is targeting a scanout
FB even if this batch is not bound to the context.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>