Bluetooth: btrtl: check for NULL in btrtl_set_quirks()

The btrtl_set_quirks() has accessed btrtl_dev->ic_info->lmp_subver since
b8e482d02513. However, if installing a Realtek Bluetooth controller
without the driver supported, it will hit the NULL point accessed.

Add a check for NULL to avoid the Kernel Oops.
Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/btrtl.c

@@ -905,6 +905,9 @@ void btrtl_set_quirks(struct hci_dev *hdev, struct btrtl_device_info *btrtl_dev)
 		break;
 	}
 
+	if (!btrtl_dev->ic_info)
+		return;
+
 	switch (btrtl_dev->ic_info->lmp_subver) {
 	case RTL_ROM_LMP_8703B:
 		/* 8723CS reports two pages for local ext features,