usb: xhci-mtk: break loop when find the endpoint to drop

No need to check the following endpoints after finding the endpoint
wanted to drop.

Fixes: 54f6a8af

 ("usb: xhci-mtk: skip dropping bandwidth of unchecked endpoints")
Cc: stable <stable@vger.kernel.org>
Reported-by: Ikjoon Jang <ikjn@chromium.org>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1612255104-5363-1-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>