fix: random: rather than entropy_store abstraction, use global (v5.17)

fix: random: rather than entropy_store abstraction, use global (v5.17)

See upstream commit :

  commit 90ed1e67e896cc8040a523f8428fc02f9b164394
  Author: Jason A. Donenfeld <Jason@zx2c4.com>
  Date:   Wed Jan 12 17:18:08 2022 +0100

    random: rather than entropy_store abstraction, use global

    Originally, the RNG used several pools, so having things abstracted out
    over a generic entropy_store object made sense. These days, there's only
    one input pool, and then an uneven mix of usage via the abstraction and
    usage via &input_pool. Rather than this uneasy mixture, just get rid of
    the abstraction entirely and have things always use the global. This
    simplifies the code and makes reading it a bit easier.

Change-Id: I1a2a14d7b6e69a047804e1e91e00fe002f757431
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>