cmd/compile: add floating point load+op operations to addressing modes pass

They were missed as part of the refactoring to use a separate
addressing modes pass.

Fixes #40426

Change-Id: Ie0418b2fac4ba1ffe720644ac918f6d728d5e420
Reviewed-on: https://go-review.googlesource.com/c/go/+/244859


Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>