drivers/char/random.c: remove unused stuct poolinfo::poolbits

commit 3bd0b5bf7dc3ea02070fcbcd682ecf628269e8ef upstream.

This field is never used, might as well remove it.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
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>