bootutil: Fix ed25519 pure signature verification

Accidentally added check for size of blen against hash length,
in bootutil_verify, was doubling check done in bootutli_verify_sig
and prevented pure signature from working.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

Author: de-nordic

boot/bootutil/src/image_ed25519.c

@@ -90,7 +90,7 @@ bootutil_verify(uint8_t *buf, uint32_t blen,
     uint8_t *pubkey;
     uint8_t *end;
 
-    if (blen != IMAGE_HASH_SIZE || slen != EDDSA_SIGNATURE_LENGTH) {
+    if (slen != EDDSA_SIGNATURE_LENGTH) {
         FIH_SET(fih_rc, FIH_FAILURE);
         goto out;
     }