freedreno/ir3: Reduce choose_instr_dec() and _inc() overhead.

freedreno/ir3: Reduce choose_instr_dec() and _inc() overhead.

If you didn't have a freed+ready instruction, you'd redo the live_effect
and check_instr() logic multiple times per instr.  Replace the multiple
loops in each function with a ranking that I think is more readable,
reducing the overhead in the process.

debugoptimized dEQP-GLES31.functional.ubo.random.all_per_block_buffers.20
runtime goes from ~3.5s -> ~3.0s on my lazor.  No shader-db change.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11855>