msm: mdss: Fix memory leaks in overlay kickoff

Add missing changes from the commit
398653b3734cd85ee1edd43acf0a11fc03014eb9. That commit is
not propagated properly to LNX.LA.3.6 branch and the
missing changes cause memory leaks during overlay kickoff
in scenarios where it is called without any data input
(i.e. during suspend/resume).

Change-Id: Ieed5bb614f0bd7d96c53fd7d24d4fddeaf2a03c4
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>