crypto/pcrypt: Replace synchronize_rcu_bh() with synchronize_rcu()

Now that synchronize_rcu() waits for bh-disable regions of code as
well as RCU read-side critical sections, the synchronize_rcu_bh() in
pcrypt_cpumask_change_notify() can be replaced by synchronize_rcu().
This commit therefore makes this change.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: <linux-crypto@vger.kernel.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>