usb: xhci-mtk: fix bandwidth release issue

This happens when @udev->reset_resume is set to true, when usb resume,
the flow as below:
  - hub_resume
    - usb_disable_interface
      - usb_disable_endpoint
        - usb_hcd_disable_endpoint
          - xhci_endpoint_disable  // it set @ep->hcpriv to NULL

Then when reset usb device, it will drop allocated endpoints,
the flow as below:
  - usb_reset_and_verify_device
    - usb_hcd_alloc_bandwidth
      - xhci_mtk_drop_ep

but @ep->hcpriv is already set to NULL, the bandwidth will be not
released anymore.

Due to the added endponts are stored in hash table, we can drop the check
of @ep->hcpriv.

Fixes: 4ce18666 ("usb: xhci-mtk: Do not use xhci's virt_dev in drop_endpoint")
Cc: stable <stable@kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20220819080556.32215-2-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-mtk-sch.c

@@ -764,8 +764,8 @@ int xhci_mtk_drop_ep(struct usb_hcd *hcd, struct usb_device *udev,
 	if (ret)
 		return ret;
 
-	if (ep->hcpriv)
-		drop_ep_quirk(hcd, udev, ep);
+	/* needn't check @ep->hcpriv, xhci_endpoint_disable set it NULL */
+	drop_ep_quirk(hcd, udev, ep);
 
 	return 0;
 }