of/fdt: avoid re-parsing '#{address,size}-cells' in of_fdt_limit_memory

Now that we initialize dt_root_addr_cells and dt_root_size_cells earlier,
use them and simplify of_fdt_limit_memory.

Link: https://lore.kernel.org/all/[e-mail]/
Signed-off-by: Rob Herring <[e-mail]>

drivers/of/fdt.c

···
 	int memory;
 	int len;
 	const void *val;
-	int nr_address_cells = OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
-	int nr_size_cells = OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
-	const __be32 *addr_prop;
-	const __be32 *size_prop;
-	int root_offset;
-	int cell_size;
-
-	root_offset = fdt_path_offset(initial_boot_params, "/");
-	if (root_offset < 0)
-		return;
-
-	addr_prop = fdt_getprop(initial_boot_params, root_offset,
-				"#address-cells", NULL);
-	if (addr_prop)
-		nr_address_cells = fdt32_to_cpu(*addr_prop);
-
-	size_prop = fdt_getprop(initial_boot_params, root_offset,
-				"#size-cells", NULL);
-	if (size_prop)
-		nr_size_cells = fdt32_to_cpu(*size_prop);
-
-	cell_size = sizeof(uint32_t)*(nr_address_cells + nr_size_cells);
+	int cell_size = sizeof(uint32_t)*(dt_root_addr_cells + dt_root_size_cells);
 
 	memory = fdt_path_offset(initial_boot_params, "/memory");
 	if (memory > 0) {