cmd/compile: fix generic inter-inter comparisons from value switch statements

cmd/compile: fix generic inter-inter comparisons from value switch statements

If value is a non-empty interface and has shape, we still need to
convert it to an interface{} first.

Fixes #53477

Change-Id: I516063ba4429a6cc24c483758387ec13815fc63e
Reviewed-on: https://go-review.googlesource.com/c/go/+/414834
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>