USB: another ehci_iaa_watchdog fix

This patch, suggested by Alan Stern, fixes the hung USB issues
on my notebook from suspend/resume cycles.

It does so by eliminating some confusion about the internal state
machine associated with unlinking from the EHCI async schedule ring,
which caused a recent regression:

  http://bugzilla.kernel.org/show_bug.cgi?id=10345

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