powerpc: Check device status before adding serial device

serial port nodes with the property status="disabled" are not usable and so
avoid adding "disabled" port with the system.
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/kernel/legacy_serial.c

@@ -330,9 +330,11 @@ void __init find_legacy_serial_ports(void)
 		if (!parent)
 			continue;
 		if (of_match_node(legacy_serial_parents, parent) != NULL) {
-			index = add_legacy_soc_port(np, np);
-			if (index >= 0 && np == stdout)
-				legacy_serial_console = index;
+			if (of_device_is_available(np)) {
+				index = add_legacy_soc_port(np, np);
+				if (index >= 0 && np == stdout)
+					legacy_serial_console = index;
+			}
 		}
 		of_node_put(parent);
 	}