aco: combine DPP into VALU before RA

aco: combine DPP into VALU before RA

Mostly helps a bunch of Cyberpunk 2077 shaders. Catches some of the cases
that the post-RA can't optimize because of register assignment.

fossil-db (Siena Cichlid):
Totals from 25 (0.02% of 150170) affected shaders:
CodeSize: 78808 -> 75764 (-3.86%)
Instrs: 14311 -> 13547 (-5.34%)
Latency: 278697 -> 277885 (-0.29%)
InvThroughput: 63428 -> 62754 (-1.06%)
Copies: 1348 -> 1349 (+0.07%); split: -0.07%, +0.15%
PreVGPRs: 1035 -> 1011 (-2.32%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11924>