ARC: [arcfpga] consolidate machine description, DT

* AA4/ML509 have same machine descriptions
* Rename simulation machine description

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/boot/dts/nsimosci.dts

@@ -27,11 +27,6 @@
 		serial0 = &uart0;
 	};
 
-	memory {
-		device_type = "memory";
-		reg = <0x80000000 0x10000000>;	/* 256M */
-	};
-
 	fpga {
 		compatible = "simple-bus";
 		#address-cells = <1>;