usb: renesas_usbhs: use delayed_work instead of work_struct

This delay is used to overjump debounce.

And, this patch also move usbhsc_drvcllbck_notify_hotplug to global,
because it will be called from other files.

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