Revert "cmd/compile: use MOVBE instruction for GOAMD64>=v3"

Revert "cmd/compile: use MOVBE instruction for GOAMD64>=v3"

This reverts CL 354670.

Reason for revert: broke make.bash with GOAMD64=v3.

Fixes #49061.

Change-Id: I7f2ed99b7c10100c4e0c1462ea91c4c9d8c609b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/356790
Trust: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Koichi Shiraishi <zchee.io@gmail.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>