cso: don't track the number of sampler states bound

cso: don't track the number of sampler states bound

This removes 2 loops from hot codepaths and adds 1 loop to a rare codepath
(restore_sampler_states), and makes sanitize_hash() slightly worse.

Sampler states, when bound, are not unbound for draw calls that don't need
them. That's OK, because bound sampler states don't add any overhead.

This results in lower CPU overhead in most cases.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>