Fix constness of the fdt void pointer in fdt_getprop_u32_default

The function fdt_getprop_u32_default doesn't modify the fdt, so it can use a
const void * for its fdt argument.

Signed-off-by: Gabe Black <gabeblack@chromium.org>

common/fdt_support.c

@@ -49,8 +49,8 @@ DECLARE_GLOBAL_DATA_PTR;
  * Convenience function to find a node and return it's property or a
  * default value if it doesn't exist.
  */
-u32 fdt_getprop_u32_default(void *fdt, const char *path, const char *prop,
-				const u32 dflt)
+u32 fdt_getprop_u32_default(const void *fdt, const char *path,
+				const char *prop, const u32 dflt)
 {
 	const u32 *val;
 	int off;

include/fdt_support.h

@@ -28,8 +28,8 @@
 
 #include <fdt.h>
 
-u32 fdt_getprop_u32_default(void *fdt, const char *path, const char *prop,
-				const u32 dflt);
+u32 fdt_getprop_u32_default(const void *fdt, const char *path,
+				const char *prop, const u32 dflt);
 int fdt_chosen(void *fdt, int force);
 int fdt_initrd(void *fdt, ulong initrd_start, ulong initrd_end, int force);
 void do_fixup_by_path(void *fdt, const char *path, const char *prop,