usb: xhci: fix interrupt transfer error happened on MTK platforms

The MTK xHCI controller use some reserved bytes in endpoint context for
bandwidth scheduling, so need keep them in xhci_endpoint_copy();

The issue is introduced by:
commit f5249461 ("xhci: Clear the host side toggle manually when
endpoint is soft reset")
It resets endpoints and will drop bandwidth scheduling parameters used
by interrupt or isochronous endpoints on MTK xHCI controller.
Fixes: f5249461

 ("xhci: Clear the host side toggle manually when
endpoint is soft reset")

Cc: stable@vger.kernel.org
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Tested-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>