UPSTREAM: random: remove the blocking pool

There is no longer any interface to read data from the blocking
pool, so remove it.

This enables quite a bit of code deletion, much of which will be
done in subsequent patches.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/511225a224bf0a291149d3c0b8b45393cd03ab96.1577088521.git.luto@kernel.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
(cherry picked from commit 90ea1c6436d26e62496616fb5891e00819ff4849)
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 148665638
Change-Id: I0ccca476cfbed9e17ab8c3bec4808adb117b57a7