iris: Stop setting up fake params

In d1c4e64a, we added a parameter to tell the back-end compiler to ignore the param array and just push however many constants you ask it to push. Iris doesn't want to push anything so it gives a bogus number of parameters and trusts the back-end compiler to dead-code all of them. This was a hack which d1c4e64a should have removed but it was left in and the back-end compiler is now pushing the requested number of registers which, because it's bogus, doesn't go well. Just get rid of the hack and the back-end compiler will do what iris wanted all along.

Fixes: d1c4e64a "intel/compiler: Add a flag to avoid compacting..."