cmd/compile: enforce strongly typed rules for ARM (6)
    
    End of "constant folding in *shift ops" until EOF
    (L1070-)
    Toolstash-check is successful.
    
    Change-Id: I55846a459aca5238f831750f04132e13a0baeed7
    Reviewed-on: https://go-review.googlesource.com/c/go/+/234198
    Reviewed-by: Giovanni Bajo <rasky@develer.com>
    Reviewed-by: Keith Randall <khr@golang.org>
    Trust: Giovanni Bajo <rasky@develer.com>
    Run-TryBot: Giovanni Bajo <rasky@develer.com>
    TryBot-Result: Go Bot <gobot@golang.org>