drm: rename driver hooks more understandably

Rename the driver hooks in the DRM to something a little more understandable:
preinit         ->      load
postinit        ->      (removed)
presetup        ->      firstopen
postsetup       ->      (removed)
open_helper     ->      open
prerelease      ->      preclose
free_filp_priv  ->      postclose
pretakedown     ->      lastclose
postcleanup     ->      unload
release         ->      reclaim_buffers_locked
version         ->      (removed)

postinit and version were replaced with generic code in the Linux DRM (drivers
now set their version numbers and description in the driver structure, like on
BSD).  postsetup wasn't used at all.  Fixes the savage hooks for
initializing and tearing down mappings at the right times.  Testing involved at
least starting X, running glxgears, killing glxgears, exiting X, and repeating.

Tested on:      FreeBSD (g200, g400, r200, r128)
                Linux (r200, savage4)

From: Eric Anholt <anholt@freebsd.org>
Signed-off-by: Dave Airlie <airlied@linux.ie>