wifi: rtw88: usb: schedule rx work after everything is set up

Right now it's possible to hit NULL pointer dereference in
rtw_rx_fill_rx_status on hw object and/or its fields because
initialization routine can start getting USB replies before
rtw_dev is fully setup.

The stack trace looks like this:

rtw_rx_fill_rx_status
rtw8821c_query_rx_desc
rtw_usb_rx_handler
...
queue_work
rtw_usb_read_port_complete
...
usb_submit_urb
rtw_usb_rx_resubmit
rtw_usb_init_rx
rtw_usb_probe

So while we do the async stuff rtw_usb_probe continues and calls
rtw_register_hw, which does all kinds of initialization (e.g.
via ieee80211_register_hw) that rtw_rx_fill_rx_status relies on.

Fix this by moving the first usb_submit_urb after everything
is set up.

For me, this bug manifested as:
[    8.893177] rtw_8821cu 1-1:1.2: band wrong, packet dropped
[    8.910904] rtw_8821cu 1-1:1.2: hw->conf.chandef.chan NULL in rtw_rx_fill_rx_status
because I'm using Larry's backport of rtw88 driver with the NULL
checks in rtw_rx_fill_rx_status.

Link: https://lore.kernel.org/linux-wireless/CA+shoWQ7P49jhQasofDcTdQhiuarPTjYEDa--NiVVx494WcuQw@mail.gmail.com/Signed-off-by: Marcin Ślusarz <mslusarz@renau.com>
Cc: Tim K <tpkuester@gmail.com>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Kalle Valo <kvalo@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20240528110246.477321-1-marcin.slusarz@gmail.com

drivers/net/wireless/realtek/rtw88/usb.c

@@ -742,7 +742,6 @@ static struct rtw_hci_ops rtw_usb_ops = {
 static int rtw_usb_init_rx(struct rtw_dev *rtwdev)
 {
 	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
-	int i;
 
 	rtwusb->rxwq = create_singlethread_workqueue("rtw88_usb: rx wq");
 	if (!rtwusb->rxwq) {
@@ -754,13 +753,19 @@ static int rtw_usb_init_rx(struct rtw_dev *rtwdev)
 
 	INIT_WORK(&rtwusb->rx_work, rtw_usb_rx_handler);
 
+	return 0;
+}
+
+static void rtw_usb_setup_rx(struct rtw_dev *rtwdev)
+{
+	struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev);
+	int i;
+
 	for (i = 0; i < RTW_USB_RXCB_NUM; i++) {
 		struct rx_usb_ctrl_block *rxcb = &rtwusb->rx_cb[i];
 
 		rtw_usb_rx_resubmit(rtwusb, rxcb);
 	}
-
-	return 0;
 }
 
 static void rtw_usb_deinit_rx(struct rtw_dev *rtwdev)
@@ -897,6 +902,8 @@ int rtw_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
 		goto err_destroy_rxwq;
 	}
 
+	rtw_usb_setup_rx(rtwdev);
+
 	return 0;
 
 err_destroy_rxwq: