ARM: dts: at91: Enable DMA on sama5d4_xplained console

BugLink: http://bugs.launchpad.net/bugs/1673538

commit ef8d02d4 upstream.

Enable DMA on usart3 to get a more reliable console. This is especially
useful for automation and kernelci were a kernel with PROVE_LOCKING enabled
is quite susceptible to character loss, resulting in tests failure.
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

arch/arm/boot/dts/at91-sama5d4_xplained.dts

@@ -110,6 +110,8 @@ slot@0 {
 			};
 
 			usart3: serial@fc00c000 {
+				atmel,use-dma-rx;
+				atmel,use-dma-tx;
 				status = "okay";
 			};