usb: host: xhci-plat: add a shutdown

usb: host: xhci-plat: add a shutdown

When loading new kernel via kexec, we need to shutdown host controller to
avoid any un-expected memory accessing during new kernel boot.

Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Cc: stable <stable@vger.kernel.org>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/r/20200306092328.41253-1-ran.wang_1@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>