drm/i915: Drop local struct_mutex around intel_init_emon[ilk]

Access to intel_init_emon() is strictly ordered by gt_powersave, using
struct_mutex around it is overkill (and will conflict with the caller
holding struct_mutex themselves).
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160909131201.16673-8-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_pm.c

@@ -6773,9 +6773,7 @@ void intel_autoenable_gt_powersave(struct drm_i915_private *dev_priv)
 
 	if (IS_IRONLAKE_M(dev_priv)) {
 		ironlake_enable_drps(dev_priv);
-		mutex_lock(&dev_priv->drm.struct_mutex);
 		intel_init_emon(dev_priv);
-		mutex_unlock(&dev_priv->drm.struct_mutex);
 	} else if (INTEL_INFO(dev_priv)->gen >= 6) {
 		/*
 		 * PCU communication is slow and this doesn't need to be