logind-util: Use %u for unsigned int in snprintf

Addresses this warning found by Denis Denisov:

  [src/logind-util.c:702]: (warning) %d in format string (no. 1)
  requires 'int' but the argument type is 'unsigned int'.

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-By: Derek Foreman <derekf@osg.samsung.com>

src/logind-util.c

@@ -702,7 +702,7 @@ weston_logind_setup_vt(struct weston_logind *wl)
 	sigset_t mask;
 	struct wl_event_loop *loop;
 
-	snprintf(buf, sizeof(buf), "/dev/tty%d", wl->vtnr);
+	snprintf(buf, sizeof(buf), "/dev/tty%u", wl->vtnr);
 	buf[sizeof(buf) - 1] = 0;
 
 	wl->vt = open(buf, O_RDWR|O_CLOEXEC|O_NONBLOCK);