drm: misc cleanup

This patch contains the following cleanups:
- make needlessly global functions static
- remove the following unused global functions:
 - drm_fops.c: drm_read
 - i915_dma.c: i915_do_cleanup_pageflip

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