x86: Add FDT SPI node for link

Add a memory-mapped 8GB SPI chip.

Signed-off-by: Simon Glass <sjg@chromium.org>

board/chromebook-x86/dts/link.dts

@@ -21,4 +21,15 @@
 
         chosen { };
         memory { device_type = "memory"; reg = <0 0>; };
+
+	spi {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "intel,ich9";
+		spi-flash@0 {
+			reg = <0>;
+			compatible = "winbond,w25q64", "spi-flash";
+			memory-map = <0xff800000 0x00800000>;
+		};
+	};
 };