usb: renesas_usbhs: prevent NULL pointer crash

usbhs_status_get_each_irq/usbhs_irq_callback_update might be called
with mod == NULL

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