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/common/image-fit.c b/common/image-fit.c
index 7ebc33e..cf4b67e 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1596,7 +1596,7 @@
 	len = (ulong)size;
 
 	/* verify that image data is a proper FDT blob */
-	if (image_type == IH_TYPE_FLATDT && fdt_check_header((char *)buf)) {
+	if (image_type == IH_TYPE_FLATDT && fdt_check_header(buf)) {
 		puts("Subimage data is not a FDT");
 		return -ENOEXEC;
 	}