aco/scheduler: Fix register demand computation for downwards moves

aco/scheduler: Fix register demand computation for downwards moves

Previously, changes in total_demand_clause were not always propagated to
total_demand. For instance, clause moves do not change the local register
demand at the end of a clause, yet they may still affect the total maximum.

Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Fixes: 8235bc64112 ("aco: try to group together VMEM loads of the same resource")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4533
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10644>