UPSTREAM: random: make /dev/random be almost like /dev/urandom

This patch changes the read semantics of /dev/random to be the same
as /dev/urandom except that reads will block until the CRNG is
ready.

None of the cleanups that this enables have been done yet.  As a
result, this gives a warning about an unused function.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/5e6ac8831c6cf2e56a7a4b39616d1732b2bdd06c.1577088521.git.luto@kernel.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
(cherry picked from commit 30c08efec8884fb106b8e57094baa51bb4c44e32)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 148665638
Change-Id: I40d6f5b535aca178419cb4f7821b4a9105367c51