drm/i915: Remove unneeded struct_mutex around rpm

We don't need struct_mutex for acquiring an rpm wakeref, and do not need
to serialise those register read (it's the wrong mutex for those
registers in any case). Begone!
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170218150050.10414-1-chris@chris-wilson.co.ukReviewed-by: Radoslaw Szwichtenberg <radoslaw.szwichtenberg@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1110,7 +1110,6 @@ DEFINE_SIMPLE_ATTRIBUTE(i915_next_seqno_fops,
 static int i915_frequency_info(struct seq_file *m, void *unused)
 {
 	struct drm_i915_private *dev_priv = node_to_i915(m->private);
-	struct drm_device *dev = &dev_priv->drm;
 	int ret = 0;
 
 	intel_runtime_pm_get(dev_priv);
@@ -1173,10 +1172,6 @@ static int i915_frequency_info(struct seq_file *m, void *unused)
 		}
 
 		/* RPSTAT1 is in the GT power well */
-		ret = mutex_lock_interruptible(&dev->struct_mutex);
-		if (ret)
-			goto out;
-
 		intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
 
 		reqf = I915_READ(GEN6_RPNSWREQ);
@@ -1211,7 +1206,6 @@ static int i915_frequency_info(struct seq_file *m, void *unused)
 		cagf = intel_gpu_freq(dev_priv, cagf);
 
 		intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
-		mutex_unlock(&dev->struct_mutex);
 
 		if (IS_GEN6(dev_priv) || IS_GEN7(dev_priv)) {
 			pm_ier = I915_READ(GEN6_PMIER);
@@ -1301,7 +1295,6 @@ static int i915_frequency_info(struct seq_file *m, void *unused)
 	seq_printf(m, "Max CD clock frequency: %d kHz\n", dev_priv->max_cdclk_freq);
 	seq_printf(m, "Max pixel clock frequency: %d kHz\n", dev_priv->max_dotclk_freq);
 
-out:
 	intel_runtime_pm_put(dev_priv);
 	return ret;
 }