Various tweaks to EHCI IRQ handling, these may affact some systems.

 - Delays enabling IRQs until the root hub is more fully set up, so
   any "resume detect" IRQs can be handled properly.  (Craig Nadler)

 - Power down ports on driver shutdown.  (Craig Nadler)

 - Remove some duplicate irq-sharing logic that somehow crept in; check
   only once, and return IRQ_NONE to detect IRQ storms better (db)

 - Minor comment fix re integrated TTs.  (db)

From:          Craig Nadler <craig.nadler@arc.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>