drm/agp: move AGP cleanup paths to drm_agpsupport.c

Introduce two new helpers, drm_agp_clear() and drm_agp_destroy() which
clear all AGP mappings and destroy the AGP head. This allows to reduce the
AGP code in core DRM and move it all to drm_agpsupport.c.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
index a7b46ff..0f54ad8 100644
--- a/drivers/gpu/drm/drm_pci.c
+++ b/drivers/gpu/drm/drm_pci.c
@@ -283,6 +283,17 @@
 	return 0;
 }
 
+static void drm_pci_agp_destroy(struct drm_device *dev)
+{
+	if (drm_core_has_AGP(dev) && dev->agp) {
+		if (drm_core_has_MTRR(dev))
+			arch_phys_wc_del(dev->agp->agp_mtrr);
+		drm_agp_clear(dev);
+		drm_agp_destroy(dev->agp);
+		dev->agp = NULL;
+	}
+}
+
 static struct drm_bus drm_pci_bus = {
 	.bus_type = DRIVER_BUS_PCI,
 	.get_irq = drm_pci_get_irq,
@@ -291,6 +302,7 @@
 	.set_unique = drm_pci_set_unique,
 	.irq_by_busid = drm_pci_irq_by_busid,
 	.agp_init = drm_pci_agp_init,
+	.agp_destroy = drm_pci_agp_destroy,
 };
 
 /**