This patch adds support for SM4 in ECB mode, i.e. skcipher ecb(sm4).

changes since v1:
- make SAFEXCEL_SM4 case entry explit, using the proper SM4_BLOCK_SIZE
  instead of "borrowing" the AES code which "coincidentally" works
Signed-off-by: Pascal van Leeuwen <pvanleeuwen@verimatrix.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>