cmd/compile/internal/types2: adjust errorcalls_test and apply it

cmd/compile/internal/types2: adjust errorcalls_test and apply it

Checker.errorf calls now have an error code and thus require at
least 4 arguments.

Change-Id: Id01c30d5d3cc747ab0b3ba4001e88985192f2d80
Reviewed-on: https://go-review.googlesource.com/c/go/+/441957
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>