usb: gadget: renesas_usbhs: remove usbhs_sys_usb_ctrl()

usbhs_sys_usb_ctrl() can collect into usbhs_sys_host/function_ctrl().

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