usb: renesas_usbhs: support multi driver

Some SuperH/board has multi USBHS on it.
This patch supports multi register for renesas_usbhs

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>