cmd/compile: use "shifted operand %s (type %s) must be integer" for some shift errors

cmd/compile: use "shifted operand %s (type %s) must be integer" for some shift errors

This matches what go/types and types2 report and it also matches
the compiler errors reported for some related shift problems.

For #55326.

Change-Id: Iee40e8d988d5a7f9ff2c49f019884d02485c9fdf
Reviewed-on: https://go-review.googlesource.com/c/go/+/436177
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>