cmd/compile: reorder rotate lowering rules in AMD64.rules

cmd/compile: reorder rotate lowering rules in AMD64.rules

These rules should belong to lowering rules not optimizations.

Change-Id: I964d2c4b1d9bef0ede572978aff01cb11bf050ac
Reviewed-on: https://go-review.googlesource.com/c/go/+/426197
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Wayne Zuo <wdvxdr@golangcn.org>