crypto: arm64 - add support for SM4 encryption using special instructions

Add support for the SM4 symmetric cipher implemented using the special
SM4 instructions introduced in ARM architecture revision 8.2.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>