rtlwifi: fix potential NULL pointer dereference

In case dev_alloc_skb fails, the fix safely returns to avoid
potential NULL pointer dereference.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtlwifi/rtl8192c/fw_common.c

@@ -623,6 +623,8 @@ void rtl92c_set_fw_rsvdpagepkt(struct ieee80211_hw *hw,
 		      u1rsvdpageloc, 3);
 
 	skb = dev_alloc_skb(totalpacketlen);
+	if (!skb)
+		return;
 	skb_put_data(skb, &reserved_page_packet, totalpacketlen);
 
 	if (cmd_send_packet)