FIT: add ability to check hashes of all images in FIT, improve output

- add function fit_all_image_check_hashes() that verifies if all
  hashes of all images in the FIT are valid
- improve output of fit_image_check_hashes() when the hash check fails

Signed-off-by: Bartlomiej Sieka <tur@semihalf.com>
diff --git a/include/image.h b/include/image.h
index 4654485..8c63686 100644
--- a/include/image.h
+++ b/include/image.h
@@ -574,6 +574,7 @@
 				int value_len);
 
 int fit_image_check_hashes (const void *fit, int noffset);
+int fit_all_image_check_hashes (const void *fit);
 int fit_image_check_os (const void *fit, int noffset, uint8_t os);
 int fit_image_check_arch (const void *fit, int noffset, uint8_t arch);
 int fit_image_check_type (const void *fit, int noffset, uint8_t type);