Bluetooth: qca: fix NULL-deref on non-serdev suspend

Qualcomm ROME controllers can be registered from the Bluetooth line
discipline and in this case the HCI UART serdev pointer is NULL.

Add the missing sanity check to prevent a NULL-pointer dereference when
wakeup() is called for a non-serdev controller during suspend.

Just return true for now to restore the original behaviour and address
the crash with pre-6.2 kernels, which do not have commit e9b3e5b
("Bluetooth: hci_qca: only assign wakeup with serial port support") that
causes the crash to happen already at setup() time.

Fixes: c1a7416 ("Bluetooth: hci_qca: Add device_may_wakeup support")
Cc: stable@vger.kernel.org      # 5.13
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/hci_qca.c

@@ -1672,6 +1672,9 @@ static bool qca_wakeup(struct hci_dev *hdev)
 	struct hci_uart *hu = hci_get_drvdata(hdev);
 	bool wakeup;
 
+	if (!hu->serdev)
+		return true;
+
 	/* BT SoC attached through the serial bus is handled by the serdev driver.
 	 * So we need to use the device handle of the serdev driver to get the
 	 * status of device may wakeup.