Can not set the @shared_hcd to NULL before decrease the usage count
by usb_put_hcd(), this will cause the shared hcd not released.

Fixes: 04284eb7 ("usb: xhci-mtk: add support runtime PM")
Cc: <stable@vger.kernel.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20221128063337.18124-1-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>