usb: renesas_usbhs: host: add endpoint user counter

renesas_usbhs attaches pipe to endpoint when urb was queued, and it will be
detached when transfer was done.  Multi device controlling was enabled by this
behavior.

Now renesas_usbhs driver tried to wait until detaching if urb was queued to
endpoint which already has been attached to pipe, and it created strange driver
behavior.

But it can re-use this attached pipe if multi urb was queued.  This patch
implements it.

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