of/fdt: Make fdt blob input parameters of unflatten functions const

Operations to unflatten fdt blobs never modify the input blobs, hence
make them const. Now we no longer need to cast arbitrary const data to
"void *" when calling of_fdt_unflatten_tree().
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/fdt.c

@@ -168,7 +168,7 @@ static void *unflatten_dt_alloc(void **mem, unsigned long size,
  * @dad: Parent struct device_node
  * @fpsize: Size of the node path up at the current depth.
  */
-static void * unflatten_dt_node(void *blob,
+static void * unflatten_dt_node(const void *blob,
 				void *mem,
 				int *poffset,
 				struct device_node *dad,
@@ -378,7 +378,7 @@ static void * unflatten_dt_node(void *blob,
  * @dt_alloc: An allocator that provides a virtual address to memory
  * for the resulting tree
  */
-static void __unflatten_device_tree(void *blob,
+static void __unflatten_device_tree(const void *blob,
 			     struct device_node **mynodes,
 			     void * (*dt_alloc)(u64 size, u64 align))
 {
@@ -441,7 +441,7 @@ static void *kernel_tree_alloc(u64 size, u64 align)
  * pointers of the nodes so the normal device-tree walking functions
  * can be used.
  */
-void of_fdt_unflatten_tree(unsigned long *blob,
+void of_fdt_unflatten_tree(const unsigned long *blob,
 			struct device_node **mynodes)
 {
 	__unflatten_device_tree(blob, mynodes, &kernel_tree_alloc);

include/linux/of_fdt.h

@@ -37,7 +37,7 @@ extern bool of_fdt_is_big_endian(const void *blob,
 				 unsigned long node);
 extern int of_fdt_match(const void *blob, unsigned long node,
 			const char *const *compat);
-extern void of_fdt_unflatten_tree(unsigned long *blob,
+extern void of_fdt_unflatten_tree(const unsigned long *blob,
 			       struct device_node **mynodes);
 
 /* TBD: Temporary export of fdt globals - remove when code fully merged */