um: Don't hardcode path as it is architecture dependent

The current code fails to run on amd64 because of hardcoded reference to
i386
Signed-off-by: NRitesh Raj Sarraf <rrs@researchut.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>

arch/um/drivers/port_user.c

@@ -168,7 +168,7 @@ int port_connection(int fd, int *socket, int *pid_out)
 {
 	int new, err;
 	char *argv[] = { "/usr/sbin/in.telnetd", "-L",
-			 "/usr/lib/uml/port-helper", NULL };
+			 OS_LIB_PATH "/uml/port-helper", NULL };
 	struct port_pre_exec_data data;
 
 	new = accept(fd, NULL, 0);