staging: rtl8723bs: fix rtw_cfg80211_monitor_if_xmit_entry's return value

A netdev xmit function should return NETDEV_TX_OK or NETDEV_TX_BUSY.
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210131183920.8514-1-martin@kaiser.cxSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8723bs/os_dep/ioctl_cfg80211.c

@@ -2516,7 +2516,7 @@ static netdev_tx_t rtw_cfg80211_monitor_if_xmit_entry(struct sk_buff *skb, struc
 
 	dev_kfree_skb_any(skb);
 
-	return 0;
+	return NETDEV_TX_OK;
 
 }