PM / OPP: add some lockdep annotations

Certain OPP APIs need to be called under RCU lock; let's add a few
rcu_lockdep_assert() calls to warn about potential misuse.

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit b02ded246d011d0eb22efc178ee711b636214083)
Signed-off-by: Alex Shi <alex.shi@linaro.org>