BACKPORT: rcu: Fix missing nocb gp wake on rcu_barrier()

In preparation for RCU lazy changes, wake up the RCU nocb gp thread if
needed after an entrain.  This change prevents the RCU barrier callback
from waiting in the queue for several seconds before the lazy callbacks
in front of it are serviced.

Reported-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
(cherry picked from commit b8f7aca3
 https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

 rcu/next)

(Backport:
Conflicts:
   kernel/rcu/tree.c
Due to missing 'rcu: Rework rcu_barrier() and callback-migration logic'
Chose not to backport that.)

Bug: 258241771
Bug: 222463781
Test: CQ
Change-Id: Ib55c5886764b74df22531eca35f076ef7acc08dd
Signed-off-by: Joel Fernandes <joelaf@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4062165


Reviewed-by: Vineeth Pillai <vineethrp@google.com>
(cherry picked from commit fc6e55ea65dca9cc52bda6081341f3fcc87f6ee7)
[Cherry picked from chromeos-5.15 tree. Minor tweaks to commit message
to match Android style]
Signed-off-by: Qais Yousef <qyousef@google.com>