gma500: make init_pm callback in struct psb_op optional

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/gma500/power.c b/drivers/gpu/drm/gma500/power.c
index bbf635c..994f669 100644
--- a/drivers/gpu/drm/gma500/power.c
+++ b/drivers/gpu/drm/gma500/power.c
@@ -58,7 +58,8 @@
 	spin_lock_init(&power_ctrl_lock);
 	mutex_init(&power_mutex);
 
-	dev_priv->ops->init_pm(dev);
+	if (dev_priv->ops->init_pm)
+		dev_priv->ops->init_pm(dev);
 }
 
 /**