wil6210: fix invalid memory access for rx_buff_mgmt debugfs

Check rx_buff_mgmt is allocated before accessing its internal fields.
Signed-off-by: Dedy Lansky <dlansky@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -1237,6 +1237,9 @@ static int wil_rx_buff_mgmt_debugfs_show(struct seq_file *s, void *data)
 	int num_active;
 	int num_free;
 
+	if (!rbm->buff_arr)
+		return -EINVAL;
+
 	seq_printf(s, "  size = %zu\n", rbm->size);
 	seq_printf(s, "  free_list_empty_cnt = %lu\n",
 		   rbm->free_list_empty_cnt);