anv: Use an anv_state for the next binding table

anv: Use an anv_state for the next binding table

This is a bit more natural because we're already getting an anv_state
most places in the pipeline.  The important part here, however, is that
we're no longer calling anv_block_pool_map on every alloc_binding_table
call.  While it's probably pretty cheap, it is potentially a linear walk
over the list of BOs and it was showing up in profiles.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>