[AGPGART] agp.h: constify struct agp_bridge_data::version

drivers/char/agp/backend.c: In function `agp_backend_initialize':
drivers/char/agp/backend.c:141: warning: assignment discards qualifiers from pointer target type

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Dave Jones <davej@redhat.com>

drivers/char/agp/agp.h

@@ -117,7 +117,7 @@ struct agp_bridge_driver {
 };
 
 struct agp_bridge_data {
-	struct agp_version *version;
+	const struct agp_version *version;
 	struct agp_bridge_driver *driver;
 	struct vm_operations_struct *vm_ops;
 	void *previous_size;