drm/msm/sde: update CWB detection logic

Modify CWB use case detection based on encoders on a crtc.
Other than wb parent encoder, if any other drm encoder is
connected to same crtc, treat wb encoder is in clone mode.

Change-Id: I05d7b52887aa01df682fe1e93a205efdcc2fa5c0
Signed-off-by: Prabhanjan Kandula <pkandula@codeaurora.org>