wil6210: check rx_buff_mgmt before accessing it

commit d6a553c0 upstream.

Make sure rx_buff_mgmt is initialized before accessing it.
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/wireless/ath/wil6210/txrx_edma.c

@@ -268,6 +268,9 @@ static void wil_move_all_rx_buff_to_free_list(struct wil6210_priv *wil,
 	struct list_head *active = &wil->rx_buff_mgmt.active;
 	dma_addr_t pa;
 
+	if (!wil->rx_buff_mgmt.buff_arr)
+		return;
+
 	while (!list_empty(active)) {
 		struct wil_rx_buff *rx_buff =
 			list_first_entry(active, struct wil_rx_buff, list);