arm: mvebu: Add SPI flash on Armada XP-GP board

This patch adds an SPI master device node for Armada XP-GP board.
This master node is an SPI flash controller 'n25q128a13'.

Since there is no 'partitions' node declared, one full sized
partition named as the device will be created.

Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Lior Amsalem <alior@marvell.com>
Tested-by: NGregory Clement <gregory.clement@free-electrons.com>
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: NGregory Clement <gregory.clement@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/boot/dts/armada-xp-gp.dts

@@ -97,5 +97,17 @@ ethernet@d0034000 {
 			phy = <&phy3>;
 			phy-mode = "rgmii-id";
 		};
+
+		spi0: spi@d0010600 {
+			status = "okay";
+
+			spi-flash@0 {
+				#address-cells = <1>;
+				#size-cells = <1>;
+				compatible = "n25q128a13";
+				reg = <0>; /* Chip select 0 */
+				spi-max-frequency = <108000000>;
+			};
+		};
 	};
 };