tegra: usb: Add support for Tegra USB peripheral

This adds basic support for the Tegra2 USB controller. Board files should
call board_usb_init() to set things up.

Configuration is performed through the FDT, with aliases used to set the
order of the ports, like this fragment:

        aliases {
		/* This defines the order of our USB ports */
                usb0 = "/usb@0xc5008000";
                usb1 = "/usb@0xc5000000";
        };

drivers/usb/host files ONLY: Acked-by: Remy Bohmer <linux@bohmer.net>
Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>