sandbox: Add and build AXI bus and device

Add test AXI drivers to the sandbox.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/arch/sandbox/dts/sandbox.dts b/arch/sandbox/dts/sandbox.dts
index 9f444c9..6ac37f1 100644
--- a/arch/sandbox/dts/sandbox.dts
+++ b/arch/sandbox/dts/sandbox.dts
@@ -11,6 +11,7 @@
 		i2c0 = &i2c_0;
 		pci0 = &pci;
 		rtc0 = &rtc_0;
+		axi0 = &axi;
 	};
 
 	chosen {
@@ -311,6 +312,16 @@
 			};
 		};
 	};
+
+	axi: axi@0 {
+		compatible = "sandbox,axi";
+		#address-cells = <0x1>;
+		#size-cells = <0x1>;
+		store@0 {
+			compatible = "sandbox,sandbox_store";
+			reg = <0x0 0x400>;
+		};
+	};
 };
 
 #include "cros-ec-keyboard.dtsi"