xhci: Fix use-after-free regression in xhci clear hub TT implementation

commit ef513be0 ("usb: xhci: Add Clear_TT_Buffer") schedules work
to clear TT buffer, but causes a use-after-free regression at the same time

Make sure hub_tt_work finishes before endpoint is disabled, otherwise
the work will dereference already freed endpoint and device related
pointers.

This was triggered when usb core failed to read the configuration
descriptor of a FS/LS device during enumeration.
xhci driver queued clear_tt_work while usb core freed and reallocated
a new device for the next enumeration attempt.

EHCI driver implents ehci_endpoint_disable() that makes sure
clear_tt_work has finished before it returns, but xhci lacks this support.
usb core will call hcd->driver->endpoint_disable() callback before
disabling endpoints, so we want this in xhci as well.

The added xhci_endpoint_disable() is based on ehci_endpoint_disable()

Fixes: ef513be0

 ("usb: xhci: Add Clear_TT_Buffer")
Cc: <stable@vger.kernel.org> # v5.3
Reported-by: Johan Hovold <johan@kernel.org>
Suggested-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Tested-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/1572013829-14044-2-git-send-email-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>