drm: possible cleanups

This patch contains the following possible cleanups:
- make the following needlessly global function static:
 - drm_bufs.c: drm_addbufs_fb()
- remove the following unused EXPORT_SYMBOL's:
 - drm_agpsupport.c: drm_agp_bind_memory
 - drm_bufs.c: drm_rmmap_locked
 - drm_bufs.c: drm_rmmap
 - drm_stub.c: drm_get_dev

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Dave Airlie <airlied@linux.ie>