nir/algebraic: optimize a*#b & -4
fossil-db (Sienna Cichlid):
Totals from 611 (0.47% of 128647) affected shaders:
CodeSize: 3096680 -> 3090976 (-0.18%)
Instrs: 570494 -> 569249 (-0.22%)
Latency: 5765865 -> 5759619 (-0.11%)
InvThroughput: 969840 -> 967608 (-0.23%)
VClause: 9690 -> 9688 (-0.02%)
Copies: 42884 -> 42894 (+0.02%); split: -0.01%, +0.03%
PreVGPRs: 28290 -> 28288 (-0.01%)