rcu/nocb: Add missing annotation for rcu_nocb_bypass_unlock()

Sparse reports warning at rcu_nocb_bypass_unlock()

warning: context imbalance in rcu_nocb_bypass_unlock() - unexpected unlock

The root cause is a missing annotation of rcu_nocb_bypass_unlock()
which causes the warning.

This commit therefore adds the missing __releases(&rdp->nocb_bypass_lock)
annotation.

Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Boqun Feng <boqun.feng@gmail.com>