crypto: cavium - make several functions static

The functions cvm_encrypt, cvm_decrypt, cvm_xts_setkey and
cvm_enc_dec_init does not need to be in global scope, so make
them static.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>