drm/vmwgfx: Nuke preclose hook

Again since the drm core takes care of event unlinking/disarming this
is now just needless code.

v2: I've completely missed eaction->fpriv_head and all the related
code. We need to nuke that too to avoid accidentally deferencing the
freed-up vmwgfx-private fpriv.

v3: Also remove vmw_fpriv->fence_events and unused variables I missed.

Cc: Thomas Hellström <thellstrom@vmware.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452548477-15905-23-git-send-email-daniel.vetter@ffwll.ch
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>