[nrf noup] bootutil: Align definitions with upstream

fixup! [nrf noup] bootutil: PureEdDSA using ED25519

Signed-off-by: Dominik Ermel <[email protected]>

Author: de-nordic

boot/bootutil/include/bootutil/image.h

@@ -102,9 +102,9 @@ struct flash_area;
 #define IMAGE_TLV_ECDSA_SIG         0x22   /* ECDSA of hash output */
 #define IMAGE_TLV_RSA3072_PSS       0x23   /* RSA3072 of hash output */
 #define IMAGE_TLV_ED25519           0x24   /* ed25519 of hash output */
-#define IMAGE_TLV_SIG_PURE          0x25   /* Whatever signature has been selected, it will be used
-                                            * as "pure" where signature is verified over entire
-                                            * image rather than hash of an image */
+#define IMAGE_TLV_SIG_PURE          0x25   /* Indicator that attached signature has been prepared
+                                            * over image rather than its digest.
+                                            */
 #define IMAGE_TLV_ENC_RSA2048       0x30   /* Key encrypted with RSA-OAEP-2048 */
 #define IMAGE_TLV_ENC_KW            0x31   /* Key encrypted with AES-KW 128 or 256*/
 #define IMAGE_TLV_ENC_EC256         0x32   /* Key encrypted with ECIES-EC256 */