cmd/internal/obj: remove unused obj.Linksymfmt

obj.Linksymfmt is no longer referenced by any packages in cmd/...

Change-Id: Id4d9213d1577e13580b60755dbf7da313b17cb0e
Reviewed-on: https://go-review.googlesource.com/41171
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/obj/sym.go

@@ -101,10 +101,3 @@ func (ctxt *Link) Int64Sym(i int64) *LSym {
 		s.Set(AttrLocal, true)
 	})
 }
-
-func Linksymfmt(s *LSym) string {
-	if s == nil {
-		return "<nil>"
-	}
-	return s.Name
-}