USB: ohci: add bus glue for the Atheros AR71XX/AR7240 SoCs

The Atheros AR71XX/AR7240 SoCs have a built-in OHCI controller.
This patch adds the necessary glue code to make the generic OHCI
driver usable for them.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>