fit: use 'const' for the input of fdt_offset() and locate_dtb_in_fit()

Those 2 functions don't modify their input, we can mark it const.
This prevents compilation warnings when they are provided const input.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

common/boot_fit.c

@@ -13,7 +13,7 @@
 #include <image.h>
 #include <libfdt.h>
 
-int fdt_offset(void *fit)
+static int fdt_offset(const void *fit)
 {
 	int images, node, fdt_len, fdt_node, fdt_offset;
 	const char *fdt_name;
@@ -55,7 +55,7 @@ int fdt_offset(void *fit)
 	return fdt_offset;
 }
 
-void *locate_dtb_in_fit(void *fit)
+void *locate_dtb_in_fit(const void *fit)
 {
 	struct image_header *header;
 	int size;

include/boot_fit.h

@@ -5,5 +5,10 @@
  * SPDX-License-Identifier:     GPL-2.0+
  */
 
-int fdt_offset(void *fit);
-void *locate_dtb_in_fit(void *fit);
+/**
+ * locate_dtb_in_fit - Find a DTB matching the board in a FIT image
+ * @fit:	pointer to the FIT image
+ *
+ * @return a pointer to a matching DTB blob if found, NULL otherwise
+ */
+void *locate_dtb_in_fit(const void *fit);