crypto: rng - Convert crypto_rng to new style crypto_type

This patch converts the top-level crypto_rng to the "new" style.
It was the last algorithm type added before we switched over
to the new way of doing things exemplified by shash.

All users will automatically switch over to the new interface.

Note that this patch does not touch the low-level interface to
rng implementations.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>