[ALPS08716617] mt6878: disp: add debug log for set dirty

[Description]
1. Add some debug logs to check abnormal trigger before leave idle done.
2. Fix coverity issues: ALPS08745115, ALPS08745120, ALPS08745123.

[Test]
MEStress Pass.

MTK-Commit-Id: 171e947a32e67defc2fda26bbac29b0335ee3d29

Signed-off-by: Kai Shi <Kai.Shi@mediatek.com>
CR-Id: ALPS08716617
Feature: display_mobile
Change-Id: I4d8ec052ef3cd9fecb1debaf70514c47ea78b906