i965: Move nir_lower_locals_to_regs a bit later.

i965: Move nir_lower_locals_to_regs a bit later.

I'm going to add a boolean scheduling pass that I want run late, but
after copy propagation and dead code elimination.  Yet, I don't want
to have to think about registers.  So, move the register conversion
a little later.

No impact on shader-db.  Suggested by Jason Ekstrand.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>