cmd/compile: log large copies on riscv64
Log large copies in the riscv64 compiler.
This was missed in
47ade08141b23cfeafed92943e16012d5dc5eb8b, resulting in
the new test added to cmd/compile/internal/logopt failing on riscv64.
Change-Id: I6f763e86f42834148e911d16928f9fbabcfa4290
Reviewed-on: https://go-review.googlesource.com/c/go/+/227804
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>