panfrost: Make block predecessor printing deterministic

Icecream95 requested to merge icecream95/mesa:deterministic into main

Reduces noise in diffs of BIFROST_MESA_DEBUG=shaders output.

The MIR printer is changed similarly.

Also remove use of global variables from the Midgard disassembler, which I noticed after getting crashes from testing the MIR patch with multi-thread shader-db.

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