Building of FIT images does not work.

The type is not set for generation of the FIT images, resulting
in no images being created without printing or returning an error
Signed-off-by: NRemy Bohmer <linux@bohmer.net>

tools/mkimage.c

@@ -229,6 +229,7 @@ main (int argc, char **argv)
 			case 'f':
 				if (--argc <= 0)
 					usage ();
+				params.type = IH_TYPE_FLATDT;
 				params.datafile = *++argv;
 				params.fflag = 1;
 				goto NXTARG;