random: remove stale maybe_reseed_primary_crng

commit 3d071d8da1f586c24863a57349586a1611b9aa67 upstream.

The function maybe_reseed_primary_crng is not used anywhere and thus can
be removed.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>