ARM: dts: Rename memory@0 to memory

zynq-7000.dtsi include skeleton.dtsi which contains memory node with
base address and size zero. If you add memory@0 node to the platform DTS
in final DTB there are two memory nodes and U-Boot works with the first
one (with zeros) which end up in failing in dram_init because size is
zero.
Platform memory node should rewrite default memory node setup from
skeleton.dtsi that's why platfroms needs to also use memory as node name
instead of memory@0.

Reported-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/dts/zynq-zc770-xm010.dts

@@ -25,7 +25,7 @@
 		stdout-path = &uart1;
 	};
 
-	memory@0 {
+	memory {
 		device_type = "memory";
 		reg = <0x0 0x40000000>;
 	};

arch/arm/dts/zynq-zc770-xm011.dts

@@ -23,7 +23,7 @@
 		stdout-path = &uart1;
 	};
 
-	memory@0 {
+	memory {
 		device_type = "memory";
 		reg = <0x0 0x40000000>;
 	};

arch/arm/dts/zynq-zc770-xm012.dts

@@ -25,7 +25,7 @@
 		stdout-path = &uart1;
 	};
 
-	memory@0 {
+	memory {
 		device_type = "memory";
 		reg = <0x0 0x40000000>;
 	};

arch/arm/dts/zynq-zc770-xm013.dts

@@ -25,7 +25,7 @@
 		stdout-path = &uart0;
 	};
 
-	memory@0 {
+	memory {
 		device_type = "memory";
 		reg = <0x0 0x40000000>;
 	};