aco: limit VALUPartialForwardingHazard search

aco: limit VALUPartialForwardingHazard search

Complicated CFG and lots of SALU can cause this to take an extremely long
time to finish.

Fixes
dEQP-VK.graphicsfuzz.cov-value-tracking-selection-dag-negation-clamp-loop
and Monster Hunter Rise demo compile times.

fossil-db (gfx1100):
Totals from 57 (0.04% of 134574) affected shaders:
Instrs: 170919 -> 171165 (+0.14%)
CodeSize: 860144 -> 861128 (+0.11%)
Latency: 961466 -> 961505 (+0.00%)
InvThroughput: 127598 -> 127608 (+0.01%)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8153
Fixes: 5806f0246fd ("aco/gfx11: workaround VALUPartialForwardingHazard")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20941>