random: group crng functions

This pulls all of the crng-focused functions into the second labeled
section.

No functional changes.

Cc: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: NDominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: NEric Biggers <ebiggers@google.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>