crypto: lrw - remove lrw_crypt()

Now that all users of lrw_crypt() have been removed in favor of the LRW
template wrapping an ECB mode algorithm, remove lrw_crypt().  Also
remove crypto/lrw.h as that is no longer needed either; and fold
'struct lrw_table_ctx' into 'struct priv', lrw_init_table() into
setkey(), and lrw_free_table() into exit_tfm().

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>