drm: remove root requirement from DRM_IOCTL_SET_VERSION (+ DRM_IOCTL_AUTH_MAGIC)

Just a DRM_MASTER flag is sufficient here, though maybe this call is
totally deprecated anyway (xf86-video-intel still calls it though).

(airlied: drop ioctl auth_magic as discussed on mailing list also)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>