mkimage: fit: add support to encrypt image with aes

This commit add the support of encrypting image with aes
in mkimage. To enable the ciphering, a node cipher with
a reference to a key and IV (Initialization Vector) must
be added to the its file. Then mkimage add the encrypted
image to the FIT and add the key and IV to the u-boot
device tree.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/Kconfig b/Kconfig
index d9be0da..caae4ae 100644
--- a/Kconfig
+++ b/Kconfig
@@ -383,6 +383,14 @@
 	  Enable this to support the pss padding algorithm as described
 	  in the rfc8017 (https://tools.ietf.org/html/rfc8017).
 
+config FIT_CIPHER
+	bool "Enable ciphering data in a FIT uImages"
+	depends on DM
+	select AES
+	help
+	  Enable the feature of data ciphering/unciphering in the tool mkimage
+	  and in the u-boot support of the FIT image.
+
 config FIT_VERBOSE
 	bool "Show verbose messages when FIT images fail"
 	help