arm: mvebu: enable the SD card slot on Armada 370 Reference Design board

The Armada 370 Reference Design board has one SD card slot, directly
connected to the SDIO IP of the SoC, so we enable this IP. there are no
GPIOs for card-detect and write-protect so we do not specify any.
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/armada-370-rd.dts

@@ -57,5 +57,12 @@ ethernet@d0074000 {
 			phy = <&phy1>;
 			phy-mode = "rgmii-id";
 		};
+
+		mvsdio@d00d4000 {
+			pinctrl-0 = <&sdio_pins1>;
+			pinctrl-names = "default";
+			status = "okay";
+			/* No CD or WP GPIOs */
+		};
 	};
 };