compat: rcu: Add support for consolidated-RCU reader checking

compat: rcu: Add support for consolidated-RCU reader checking

Upstream commit:
    commit 28875945ba98d1b47a8a706812b6494d165bb0a0
    Author: Joel Fernandes (Google) <joel@joelfernandes.org>
    Date:   Tue Jul 16 18:12:22 2019 -0400

    rcu: Add support for consolidated-RCU reader checking

    This commit adds RCU-reader checks to list_for_each_entry_rcu() and
    hlist_for_each_entry_rcu().  These checks are optional, and are indicated
    by a lockdep expression passed to a new optional argument to these two
    macros.  If this optional lockdep expression is omitted, these two macros
    act as before, checking for an RCU read-side critical section.

    Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
    [ paulmck: Update to eliminate return within macro and update comment. ]
    Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Backport portion of upstream commit for hlist_for_each_entry_rcu() macro
so that it can be used in following bug fix.

Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>