Documentation: PM: Add SPDX license tags to multiple files

Add SPDX license tags to .rst files under Documentation/driver-api/pm
and Documentation/admin-quide/pm.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>

Documentation/admin-guide/pm/cpufreq.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 .. |struct cpufreq_policy| replace:: :c:type:`struct cpufreq_policy <cpufreq_policy>`
 .. |intel_pstate| replace:: :doc:`intel_pstate <intel_pstate>`
 

Documentation/admin-guide/pm/cpuidle.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 .. |struct cpuidle_state| replace:: :c:type:`struct cpuidle_state <cpuidle_state>`
 .. |cpufreq| replace:: :doc:`CPU Performance Scaling <cpufreq>`
 

Documentation/admin-guide/pm/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ================
 Power Management
 ================

Documentation/admin-guide/pm/intel_pstate.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ===============================================
 ``intel_pstate`` CPU Performance Scaling Driver
 ===============================================

Documentation/admin-guide/pm/sleep-states.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ===================
 System Sleep States
 ===================

Documentation/admin-guide/pm/strategies.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ===========================
 Power Management Strategies
 ===========================

Documentation/admin-guide/pm/system-wide.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ============================
 System-Wide Power Management
 ============================

Documentation/admin-guide/pm/working-state.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ==============================
 Working-State Power Management
 ==============================

Documentation/driver-api/pm/cpuidle.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 .. |struct cpuidle_governor| replace:: :c:type:`struct cpuidle_governor <cpuidle_governor>`
 .. |struct cpuidle_device| replace:: :c:type:`struct cpuidle_device <cpuidle_device>`
 .. |struct cpuidle_driver| replace:: :c:type:`struct cpuidle_driver <cpuidle_driver>`

Documentation/driver-api/pm/devices.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 .. |struct dev_pm_ops| replace:: :c:type:`struct dev_pm_ops <dev_pm_ops>`
 .. |struct dev_pm_domain| replace:: :c:type:`struct dev_pm_domain <dev_pm_domain>`
 .. |struct bus_type| replace:: :c:type:`struct bus_type <bus_type>`

Documentation/driver-api/pm/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ===============================
 CPU and Device Power Management
 ===============================

Documentation/driver-api/pm/notifiers.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 =============================
 Suspend/Hibernation Notifiers
 =============================

Documentation/driver-api/pm/types.rst

+.. SPDX-License-Identifier: GPL-2.0
+
 ==================================
 Device Power Management Data Types
 ==================================