USB: at91: modify OHCI driver to allow shared interrupts

At91sam9g45 series has a set of high speed USB interfaces.
The host driver is an EHCI with its companion OHCI. OHCI is
always handled by ohci-at91.c.
This wrapper is just modified to allow IRQ sharing
between two controllers.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>