aco: add affinity for non-sequential MIMG operands

aco: add affinity for non-sequential MIMG operands

fossil-db (GFX10.3):
Totals from 42008 (30.14% of 139391) affected shaders:
VGPRs: 2139116 -> 2147696 (+0.40%); split: -0.06%, +0.46%
CodeSize: 199109120 -> 198637852 (-0.24%); split: -0.24%, +0.01%
Instrs: 37713901 -> 37714574 (+0.00%); split: -0.02%, +0.03%
Cycles: 1621911328 -> 1621634168 (-0.02%); split: -0.02%, +0.01%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8523>