arm: mvebu: Add SPI flash on Armada 370 DB board

This patch add support for the SPI flash MX25l25635E which is present
on the Armada 370 DB board. This flash stores the bootloader and its
environment.
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

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

@@ -82,5 +82,17 @@ usb@d0050000 {
 		usb@d0051000 {
 			status = "okay";
 		};
+
+		spi0: spi@d0010600 {
+			status = "okay";
+
+			spi-flash@0 {
+				#address-cells = <1>;
+				#size-cells = <1>;
+				compatible = "mx25l25635e";
+				reg = <0>; /* Chip select 0 */
+				spi-max-frequency = <50000000>;
+			};
+		};
 	};
 };