getprotoent_r: use correct define for return value

Doesn't correctly set result=NULL on error or EOF.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/inet/getproto.c

@@ -144,7 +144,7 @@ int getprotoent_r(struct protoent *result_buf,
     }
 again:
     if ((p = fgets(line, BUFSIZ, protof)) == NULL) {
-	rv=TRY_AGAIN;
+	rv=ENOENT;
 	goto DONE;
     }