RRM: Remove unnecessary cb check

There is only a single caller for wpas_rrm_send_neighbor_rep_request()
and it unconditionally uses a callback function, so cb cannot be NULL
here and there is no need for additional complexity and extra code size
to check for it explicitly.

Signed-off-by: Jouni Malinen <j@w1.fi>

wpa_supplicant/rrm.c

@@ -160,12 +160,6 @@ int wpas_rrm_send_neighbor_rep_request(struct wpa_supplicant *wpa_s,
 		return -EOPNOTSUPP;
 	}
 
-	if (!cb) {
-		wpa_printf(MSG_DEBUG,
-			   "RRM: Neighbor Report request must provide a callback.");
-		return -EINVAL;
-	}
-
 	/* Refuse if there's a live request */
 	if (wpa_s->rrm.notify_neighbor_rep) {
 		wpa_printf(MSG_DEBUG,