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/include/drm/drmP.h b/include/drm/drmP.h
index 1a4eba6..fba5473 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -736,6 +736,7 @@
 	int (*irq_by_busid)(struct drm_device *dev, struct drm_irq_busid *p);
 	/* hooks that are for PCI */
 	int (*agp_init)(struct drm_device *dev);
+	void (*agp_destroy)(struct drm_device *dev);
 
 };
 
@@ -1453,6 +1454,8 @@
 
 				/* AGP/GART support (drm_agpsupport.h) */
 extern struct drm_agp_head *drm_agp_init(struct drm_device *dev);
+extern void drm_agp_destroy(struct drm_agp_head *agp);
+extern void drm_agp_clear(struct drm_device *dev);
 extern int drm_agp_acquire(struct drm_device *dev);
 extern int drm_agp_acquire_ioctl(struct drm_device *dev, void *data,
 				 struct drm_file *file_priv);