aco/gfx11: optimize dual source export

aco/gfx11: optimize dual source export

We can combine dpp with the v_cndmask_b32.

Foz-DB Navi31:
Totals from 222 (0.28% of 79330) affected shaders:
Instrs: 564392 -> 563373 (-0.18%); split: -0.19%, +0.01%
CodeSize: 2867040 -> 2864728 (-0.08%); split: -0.09%, +0.01%
Latency: 4278957 -> 4275199 (-0.09%); split: -0.09%, +0.00%
InvThroughput: 586636 -> 585824 (-0.14%); split: -0.14%, +0.00%
SClause: 20210 -> 20211 (+0.00%); split: -0.02%, +0.02%
Copies: 39763 -> 39778 (+0.04%); split: -0.13%, +0.17%
PreVGPRs: 13924 -> 13922 (-0.01%)

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25541>