drm/msm: fix bug after preclose removal

commit 53190c71
Author:     Daniel Vetter <daniel.vetter@ffwll.ch>
AuthorDate: Mon Jan 25 22:16:49 2016 +0100
Commit:     Daniel Vetter <daniel.vetter@ffwll.ch>
CommitDate: Mon Feb 8 09:55:50 2016 +0100

    drm/msm: Nuke preclose hooks

Left around the unused (and null) preclose fxn ptr, and things
predictibly explode when you try to call that.

Signed-off-by: Rob Clark <robdclark@gmail.com>