Previously, i965/iris tried to reuse the currently programmed URB config
if it was good enough for BLORP, rather than reprogramming it each time.
However, this will make some things harder on Gen12+ and we've not seen
any performance impact from emitting URB more frequently in ANV.

This makes the blorp <-> driver interface a bit simpler on Gen7+ because
now all the driver has to do is to provide the L3$ config rather than
trying to hand off URB re-config to blorp.

Cc: "20.0" mesa-stable@lists.freedesktop.org
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <!3454>