USB: EHCI: add need_io_watchdog flag to ehci_hcd

Basically the io watchdog is only useful for those quirk HCDs. For most
good ones, it only brings unnecessary wakeups.  At least, I know the
Intel EHCI HCDs should turn off the flag.

Signed-off-by: Alek Du <alek.du@intel.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>