mips: ralink: convert to use unflatten_and_copy_device_tree

The ralink FDT code can be simplified by using
unflatten_and_copy_device_tree function. This removes all accesses to
FDT header data by the arch code.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Tested-by: Grant Likely <grant.likely@linaro.org>

arch/mips/ralink/of.c

@@ -52,30 +52,7 @@ __iomem void *plat_of_remap_node(const char *node)
 
 void __init device_tree_init(void)
 {
-	unsigned long base, size;
-	void *fdt_copy;
-
-	if (!initial_boot_params)
-		return;
-
-	base = virt_to_phys((void *)initial_boot_params);
-	size = be32_to_cpu(initial_boot_params->totalsize);
-
-	/* Before we do anything, lets reserve the dt blob */
-	reserve_bootmem(base, size, BOOTMEM_DEFAULT);
-
-	/* The strings in the flattened tree are referenced directly by the
-	 * device tree, so copy the flattened device tree from init memory
-	 * to regular memory.
-	 */
-	fdt_copy = alloc_bootmem(size);
-	memcpy(fdt_copy, initial_boot_params, size);
-	initial_boot_params = fdt_copy;
-
-	unflatten_device_tree();
-
-	/* free the space reserved for the dt blob */
-	free_bootmem(base, size);
+	unflatten_and_copy_device_tree();
 }
 
 void __init plat_mem_setup(void)