usb: gadget: atmel: remove unused DMA_ADDR_INVALID

DMA_ADDR_INVALID isn't (and shouldn't) be used
anymore, let's remove it.
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/atmel_usba_udc.h

@@ -216,12 +216,6 @@
 #define EP0_EPT_SIZE		USBA_EPT_SIZE_64
 #define EP0_NR_BANKS		1
 
-/*
- * REVISIT: Try to eliminate this value. Can we rely on req->mapped to
- * provide this information?
- */
-#define DMA_ADDR_INVALID (~(dma_addr_t)0)
-
 #define FIFO_IOMEM_ID	0
 #define CTRL_IOMEM_ID	1