panfrost: Allocate tiler and scratchpad BOs per-batch

panfrost: Allocate tiler and scratchpad BOs per-batch

If we want to execute several batches in parallel they need to have
their own tiler and scratchpad BOs. Let move those objects to
panfrost_batch and allocate them on a per-batch basis.

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