[PATCH] USB: EHCI unlink tweaks

This patch modifies the behavior of the EHCI driver in an unlink path
that seems to be causing various issues on some systems.  Those problems
have included issues with disconnection, driver unbinding, and similar
cases where urb unlinking would just not work right.

This patch should help avoid those problems by not turning off the async
(control/bulk) schedule until it's not expecting an "async advance" IRQ,
which comes from the processing passing the schedule head.  Whether the
driver attempts to do such things is dependent on system timings, so
many folk would never have seen these problems.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>