cmd/compile: use yyerrorl in some typechecking functions

Replace usage of yyerror with yyerrorl in checkdefergo and copytype in
typecheck.go.

All covered error messages already appear in the tests and the yyerror
replacement did not lead to any tests failing.

Passes toolstash-check

Updates #19683

Change-Id: I735e83bcda7ddc6a14afb22e50200bcbb9192fc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/69910
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/typecheck.go

@@ -2204,7 +2204,7 @@ func checkdefergo(n *Node) {
 		if n.Left.Orig != nil && n.Left.Orig.Op == OCONV {
 			break
 		}
-		yyerror("%s discards result of %v", what, n.Left)
+		yyerrorl(n.Pos, "%s discards result of %v", what, n.Left)
 		return
 	}
 
@@ -2218,7 +2218,7 @@ func checkdefergo(n *Node) {
 		// The syntax made sure it was a call, so this must be
 		// a conversion.
 		n.SetDiag(true)
-		yyerror("%s requires function call, not conversion", what)
+		yyerrorl(n.Pos, "%s requires function call, not conversion", what)
 	}
 }