i965: Fix massive memory allocation for streaming texture usage.

i965: Fix massive memory allocation for streaming texture usage.

Once we've freed a miptree, we won't see any more state cache requests
that would hit the things that pointed at it until we've let the miptree
get released back into the BO cache to be reused.  By leaving those
surface state and binding table pointers that pointed at it around, we
would end up with up to (500 * texture size) in memory uselessly consumed
by the state cache.

Bug #20057
Bug #23530