[ALPS08770811] mdp:fix mdp memory stepping issue

[Description]
When mdp is wait complete, if go to close
mdp node, there will be memory stepping.

[Test]
Pass mdp vulscan test.

MTK-Commit-Id: 6967747f2dc656a33bbd4582b1998567d2d825ee

Signed-off-by: LiaoHui <ot_hui.liao@mediatek.com>
CR-Id: ALPS08770811
Feature: mdp driver
Change-Id: I516ae846b495dd30f83f660d225b583052566d72