pan/midgard: Call scheduler/RA in a loop

pan/midgard: Call scheduler/RA in a loop

This will allow us to insert instructions as a result of register
allocation, permitting spilling to be implemented. As a side effect,
with the assert commented out this would fix a bunch of glamor crashes
(due to RA failures) so MATE becomes useable.

Ideally we'll have scheduling or RA actually sorted out before the
branch point but if not this gives us a one-line out to get X working...

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>