Fix memory leak in ed25519_openssh_createkey

If q could not be read from the input blob, the allocated ec_key
structure was not freed.

sshecc.c

@@ -2029,10 +2029,10 @@ static void *ed25519_openssh_createkey(const struct ssh_signkey *self,
     }
 
     getstring((const char**)blob, len, &q, &qlen);
-    if (!q)
-        return NULL;
-    if (qlen != 64)
+    if (!q || qlen != 64) {
+        ecdsa_freekey(ec);
         return NULL;
+    }
 
     ec->privateKey = bignum_from_bytes_le((const unsigned char *)q, 32);