ecc: Fix _gcry_ecc_mont_decodepoint for data by old implementation.
* cipher/ecc-misc.c (_gcry_ecc_mont_decodepoint): Support data by old implementation by opaque public key. Fix confusion of endian, in the handling of data by normal MPI key.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>