usb: gadget: udc: atmel: Remove obsolete include

The include defines the private platform_data structure used with AVR
platforms. It has no user since 7c55984e

. Remove it.

Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>