usb: gadget: lpc32xx_udc: Support multiple controllers

The lpc32xx_udc driver supported only one controller by defining a global
static struct for it. This patch enables multiple instances of the controller
by dynamic allocation of the struct at probe(). A static struct is kept as a
template on initialization since it does some complex preset, reflecting fixed
hardware endpoint structure.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>