disp: msm: sde: clear cwb_enc_mask post in_clone_mode is set

Add changes to clear the cwb_enc_mask in sde_crtc_state post
phys_enc->in_clone_mode is set. This is required to avoid
race issues seen when cwb gets enabled in alternate commits.

Change-Id: I555cc0401b3200f7e8bcc6be8884d04cb3ce69fb
Signed-off-by: Jayaprakash Madisetty <jmadiset@codeaurora.org>