Revert "xhci: plat: Register shutdown for xhci_plat"

This reverts commit b07c1251

It is incomplete and causes hangs on devices when shutting down.  It
needs a much more "complete" fix in order to work properly.  As that fix
has not been merged, revert this patch for now before it causes any more
problems.

Cc: Greg Hackmann <ghackmann@google.com>
Cc: Adam Wallis <awallis@codeaurora.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>