ARM: dts: aspeed: ast2500: Update flash layout

Move to the openbmc-flash-layout.dtsi file.
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-ast2500-evb.dts

@@ -27,6 +27,7 @@ flash@0 {
 		status = "okay";
 		m25p,fast-read;
 		label = "bmc";
+#include "openbmc-flash-layout.dtsi"
 	};
 };