ir3: Use the new NIR lowering pass for integer multiplication

ir3: Use the new NIR lowering pass for integer multiplication

Shader-db stats courtesy of Eric Anholt:

total instructions in shared programs: 6480215 -> 6475457 (-0.07%)
instructions in affected programs: 662105 -> 657347 (-0.72%)
helped: 1209
HURT: 13
total constlen in shared programs: 1432704 -> 1427769 (-0.34%)
constlen in affected programs: 100063 -> 95128 (-4.93%)
helped: 512
HURT: 0
total max_sun in shared programs: 875561 -> 873387 (-0.25%)
max_sun in affected programs: 46179 -> 44005 (-4.71%)
helped: 1087
HURT: 0

Reviewed-by: Eric Anholt <eric@anholt.net>