disp: msm: sde: clear dim_layers as part of null commit

Add changes to clear any dim_layers present in the crtc_state
as part of null commit.

Change-Id: Iaa5d01d7d512445e1524bac85012adda6be6c4a9
Signed-off-by: Jayaprakash <jmadiset@codeaurora.org>