drm/i915/psr: Avoid initializing PSR if there is no sink support.

DPCD read for the eDP is complete by the time intel_psr_init() is
called, which means we can avoid initializing PSR structures and state
if there is no sink support.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180103213824.1405-3-dhinakaran.pandiyan@intel.com
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 6890340..cc659b4 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2521,14 +2521,19 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
 	u32 stat[3];
 	enum pipe pipe;
 	bool enabled = false;
+	bool sink_support;
 
 	if (!HAS_PSR(dev_priv))
 		return -ENODEV;
 
+	sink_support = dev_priv->psr.sink_support;
+	seq_printf(m, "Sink_Support: %s\n", yesno(sink_support));
+	if (!sink_support)
+		return 0;
+
 	intel_runtime_pm_get(dev_priv);
 
 	mutex_lock(&dev_priv->psr.lock);
-	seq_printf(m, "Sink_Support: %s\n", yesno(dev_priv->psr.sink_support));
 	seq_printf(m, "Enabled: %s\n", yesno((bool)dev_priv->psr.enabled));
 	seq_printf(m, "Active: %s\n", yesno(dev_priv->psr.active));
 	seq_printf(m, "Busy frontbuffer bits: 0x%03x\n",