staging: rtl8822be: fix missing null check on dev_alloc_skb return

dev_alloc_skb can potentially return NULL, so add a null check to
avoid a null pointer dereference on skb

Detected by CoverityScan, CID#1454558 ("Dereference on null return")

Fixes: 7e5b796cde7e ("staging: r8822be: Add the driver code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtlwifi/rtl8822be/fw.c

@@ -464,6 +464,8 @@ bool rtl8822b_halmac_cb_write_data_rsvd_page(struct rtl_priv *rtlpriv, u8 *buf,
 	int count;
 
 	skb = dev_alloc_skb(size);
+	if (!skb)
+		return false;
 	memcpy((u8 *)skb_put(skb, size), buf, size);
 
 	if (!_rtl8822be_send_bcn_or_cmd_packet(rtlpriv->hw, skb, BEACON_QUEUE))