[new uImage] Add node offsets for FIT images listed in struct bootm_headers

This patch adds new node offset fields to struct bootm_headers
and updates bootm_headers processing code to make use of them.
Saved node offsets allow to avoid repeating fit_image_get_node() calls.

Signed-off-by: Marian Balakowicz <m8@semihalf.com>
diff --git a/common/image.c b/common/image.c
index 6458fb1..e838f65 100644
--- a/common/image.c
+++ b/common/image.c
@@ -891,6 +891,7 @@
 
 			images->fit_hdr_rd = fit_hdr;
 			images->fit_uname_rd = fit_uname_ramdisk;
+			images->fit_noffset_rd = rd_noffset;
 			break;
 #endif
 		default: