Revert "EC_KEY_priv2buf (): check parameter sanity"

This reverts commit acae59bb.
Reviewed-by: NDr. Stephen Henson <steve@openssl.org>

crypto/ec/ec_key.c

@@ -583,8 +583,8 @@ size_t EC_KEY_priv2buf(const EC_KEY *eckey, unsigned char **pbuf)
     size_t len;
     unsigned char *buf;
     len = EC_KEY_priv2oct(eckey, NULL, 0);
-    if (len == 0 || pbuf == NULL)
-        return len;
+    if (len == 0)
+        return 0;
     buf = OPENSSL_malloc(len);
     if (buf == NULL)
         return 0;