aco: follow through temporary when merging tests into constant comparisons

aco: follow through temporary when merging tests into constant comparisons

This can happen with v_mov_b32(s_mov_b32(literal))

pipeline-db (Navi):
Totals from affected shaders:
SGPRS: 632 -> 632 (0.00 %)
VGPRS: 492 -> 492 (0.00 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 77488 -> 76928 (-0.72 %) bytes
Max Waves: 67 -> 67 (0.00 %)
Instructions: 14426 -> 14332 (-0.65 %)

pipeline-db (Vega):
Totals from affected shaders:
SGPRS: 632 -> 632 (0.00 %)
VGPRS: 492 -> 492 (0.00 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 77512 -> 76952 (-0.72 %) bytes
Max Waves: 67 -> 67 (0.00 %)
Instructions: 14432 -> 14338 (-0.65 %)

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/2883>