vc4: Make vc4_qir_schedule handle each block in the program.

vc4: Make vc4_qir_schedule handle each block in the program.

Basically we just treat each block independently.  The only inter-block
scheduling I can think of that would be be interesting would be to move
texture result collection to after a short loop/if block that doesn't do
texturing.  However, the kernel disallows that as part of its security
validation.