arc: use unflatten_and_copy_device_tree

Use the common unflatten_and_copy_device_tree to copy the built-in FDT
out of init section.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Grant Likely <grant.likely@linaro.org>

arch/arc/kernel/setup.c

@@ -346,8 +346,7 @@ void __init setup_arch(char **cmdline_p)
 	setup_arch_memory();
 
 	/* copy flat DT out of .init and then unflatten it */
-	copy_devtree();
-	unflatten_device_tree();
+	unflatten_and_copy_device_tree();
 
 	/* Can be issue if someone passes cmd line arg "ro"
 	 * But that is unlikely so keeping it as it is