drm/i915: Balance assert_rpm_wakelock_held() for !IS_ENABLED(CONFIG_PM)

drm/i915: Balance assert_rpm_wakelock_held() for !IS_ENABLED(CONFIG_PM)

commit 09731280028ce03e6a27e1998137f1775a2839f3
Author: Imre Deak <imre.deak@intel.com>
Date:   Wed Feb 17 14:17:42 2016 +0200

    drm/i915: Add helper to get a display power ref if it was already enabled

left the rpm wakelock assertions unbalanced if CONFIG_PM was disabled as
intel_runtime_pm_get_if_in_use() would return true without incrementing
the local bookkeeping required for the assertions.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
CC: Mika Kuoppala <mika.kuoppala@intel.com>
CC: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1456434628-22574-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Imre Deak <imre.deak@intel.com>