usb: renesas_usbhs: gadget: disable all eps when the driver stops

A gadget driver will not disable eps immediately when ->disconnect()
is called. But, since this driver assumes all eps stop after
the ->disconnect(), unexpected behavior happens (especially in system
suspend).
So, this patch disables all eps in usbhsg_try_stop(). After disabling
eps by renesas_usbhs driver, since some functions will be called by
both a gadget and renesas_usbhs driver, renesas_usbhs driver should
protect uep->pipe. To protect uep->pipe easily, this patch adds a new
lock in struct usbhsg_uep.

Fixes: 2f98382d ("usb: renesas_usbhs: Add Renesas USBHS Gadget")
Cc: <stable@vger.kernel.org> # v3.0+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>