cmd/compile/internal/ssa: wire up late lower block function

cmd/compile/internal/ssa: wire up late lower block function

Currently, the lowerBlock function is reused with lateLowerValue, meaning
that any block rewriting rules in the late lower pass are silently ignored.
Change the late lower pass to actually use the lateLowerBlock function with
the lateLowerValue function.

Change-Id: Iaac1c2955bb27078378cac50cde3716e79a7d9f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/444335
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>