BACKPORT: FROMGIT: 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>

(Backport: Adjustments due to changes in how wake_nocb_gp() locks)

(cherry picked from commit b8f7aca3
 https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

 rcu/next)

BUG=b:222463781
TEST=powerIdle lab tests.

Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Parshuram Sangle <parshuram.sangle@intel.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3965070


Reviewed-by: Ross Zwisler <zwisler@google.com>
Change-Id: I830269cd41b18862a1a58b26ce3292c6c4457bc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4067578