drm/fsl: Remove preclose hook

Doesn't do anything, but annoys when auditing them all.

Cc: Jianwei Wang <jianwei.wang.chn@gmail.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452548477-15905-7-git-send-email-daniel.vetter@ffwll.ch


Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>