cmd/compile: use callsite as line number for argument marshaling

cmd/compile: use callsite as line number for argument marshaling

Don't use the line number of the argument itself, as that may be from
arbitrarily earlier in the function.

Fixes #60673

Change-Id: Ifc0a2aaae221a256be3a4b0b2e04849bae4b79d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/502656
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>