usb: gadget: renesas_usbhs: modify function name of usbhs_set_device_xx()

it was device configuration setting function, not only speed.
This patch modify function name usbhs_set_device_speed() -> usbhs_set_device_config()

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>