cmd/compile: implement constant rotates on arm64

cmd/compile: implement constant rotates on arm64

Explicit constant rotates work, but constant arguments to
bits.RotateLeft* needed the additional rule.

Fixes #48465

Change-Id: Ia7544f21d0e7587b6b6506f72421459cd769aea6
Reviewed-on: https://go-review.googlesource.com/c/go/+/350909
Trust: Keith Randall <khr@golang.org>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>