drm/i915: add runtime PM get/put call in i915_execlists

Otherwise we will get WARNs when we read context status registers and
the machine is suspended.

Testcase: igt/pm_rpm/debugfs-read
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -1848,6 +1848,8 @@ static int i915_execlists(struct seq_file *m, void *data)
 	if (ret)
 		return ret;
 
+	intel_runtime_pm_get(dev_priv);
+
 	for_each_ring(ring, dev_priv, ring_id) {
 		struct intel_ctx_submit_request *head_req = NULL;
 		int count = 0;
@@ -1899,6 +1901,7 @@ static int i915_execlists(struct seq_file *m, void *data)
 		seq_putc(m, '\n');
 	}
 
+	intel_runtime_pm_put(dev_priv);
 	mutex_unlock(&dev->struct_mutex);
 
 	return 0;