cmd/compile: reenable name preservation on copies in expand_calls

cmd/compile: reenable name preservation on copies in expand_calls

This reverts CL 311829, and reenables CL 309330. The issue
should be fixed in the previous CL.

Change-Id: I69db0565c72470a1814f135d8f8ec62c781bfc5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/312094
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>