image: Rename fit_add_hashes() to fit_add_verification_data()

We intend to add signatures to FITs also, so rename this function so that
it is not specific to hashing. Also rename fit_image_set_hashes() and
make it static since it is not used outside this file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>
diff --git a/include/image.h b/include/image.h
index 6d7cd54..f82d709 100644
--- a/include/image.h
+++ b/include/image.h
@@ -614,8 +614,14 @@
 				int *value_len);
 
 int fit_set_timestamp(void *fit, int noffset, time_t timestamp);
-int fit_set_hashes(void *fit);
-int fit_image_set_hashes(void *fit, int image_noffset);
+
+/**
+ * fit_add_verification_data() - Calculate and add hashes to FIT
+ *
+ * @fit:	Fit image to process
+ * @return 0 if ok, <0 for error
+ */
+int fit_add_verification_data(void *fit);
 
 int fit_image_verify(const void *fit, int noffset);
 int fit_all_image_verify(const void *fit);