cmd/compile/internal/ir: mark Addrtaken in NewAddrExpr

cmd/compile/internal/ir: mark Addrtaken in NewAddrExpr

This CL changes NewAddrExpr to require its operand to always be
typechecked, so it can return an appropriately typechecked node and
mark Addrtaken as appropriate in the process.

Change-Id: I97c1f29305a9abfda35c42a43561c4c15fb5b52e
Reviewed-on: https://go-review.googlesource.com/c/go/+/522879
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>