ARM: at91: sama5d4: dtsi: usba ep7 support dma

The endpoint 7 of usb high device port supports dma operation.
So, add "atmel,can-dma" property to it.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>