disp: msm: sde: add scaler3_cfg and pixel_ext to sde plane

Add scaler3_cfg and pixel_ext to sde plane to avoid updating state
variables in commit thread. This fixes atomic check failure when
scaler lut is not set.

Change-Id: I936b124ca6f90af22a87df31536204e837422a70
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>