vc4: Use the ra_alloc_contig_reg_class() function to speed up RA.

It means we don't need to do the n^2 loop over the regs to set up the pq
values, nor do we need to allocate conflicts lists.

Acked-by: Erico Nunes <nunes.erico@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9437>
1 file changed