FIT: delete unnecessary casts

Becuase fdt_check_header function takes (const void *)
type argument, the argument should be passed to it
without being casted to (char *).

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/tools/fit_image.c b/tools/fit_image.c
index 47beaaf..0400a60 100644
--- a/tools/fit_image.c
+++ b/tools/fit_image.c
@@ -23,7 +23,7 @@
 static int fit_verify_header (unsigned char *ptr, int image_size,
 			struct mkimage_params *params)
 {
-	return fdt_check_header ((void *)ptr);
+	return fdt_check_header(ptr);
 }
 
 static int fit_check_image_types (uint8_t type)