staging:rtl8188eu Fix comparison to NULL

This patch replaces the comparison of variable say x to NULL with  '!x'
signed-off-by: Janani Sankara Babu <jananis37@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/core/rtw_mlme.c

@@ -1502,7 +1502,7 @@ int rtw_select_and_join_from_scanned_queue(struct mlme_priv *pmlmepriv)
 	pmlmepriv->pscanned = phead->next;
 	while (phead != pmlmepriv->pscanned) {
 		pnetwork = container_of(pmlmepriv->pscanned, struct wlan_network, list);
-		if (pnetwork == NULL) {
+		if (!pnetwork) {
 			RT_TRACE(_module_rtl871x_mlme_c_, _drv_err_, ("%s return _FAIL:(pnetwork==NULL)\n", __func__));
 			ret = _FAIL;
 			goto exit;