drm/i915: parse child device from VBT

On some laptops there is no HDMI/DP. But the xrandr still reports
several disconnected HDMI/display ports. In such case the user will be
confused.
 >DVI1 disconnected (normal left inverted right x axis y axis)
 >DP1 disconnected (normal left inverted right x axis y axis)
 >DVI2 disconnected (normal left inverted right x axis y axis)
 >DP2 disconnected (normal left inverted right x axis y axis)
 >DP3 disconnected (normal left inverted right x axis y axis)

This patch set is to use the child device parsed in VBT to decide whether
the HDMI/DP/LVDS/TV should be initialized.

Parse the child device from VBT.

The device class type is also added for LFP, TV, HDMI, DP output.

https://bugs.freedesktop.org/show_bug.cgi?id=22785

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 093146b..a8efe78 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1526,6 +1526,15 @@
 	}
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		/*
+		 * free the memory space allocated for the child device
+		 * config parsed from VBT
+		 */
+		if (dev_priv->child_dev && dev_priv->child_dev_num) {
+			kfree(dev_priv->child_dev);
+			dev_priv->child_dev = NULL;
+			dev_priv->child_dev_num = 0;
+		}
 		drm_irq_uninstall(dev);
 		vga_client_register(dev->pdev, NULL, NULL, NULL);
 	}