drivers/char/drm/drm_memory.c: possible cleanups

- #if 0 the following unused global function:
  - drm_ioremap_nocache()

- make the following needlessly global functions static:
  - agp_remap()
  - drm_lookup_map()

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@osdl.org>