usb: ohci-platform: Enable optional use of reset controller

The OHCI controllers used in the Allwinner A31 are asserted in reset using a
global reset controller.

Add optional support for such a controller in the OHCI platform driver.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>