drm/msm/sde: Add new API to check clone mode

CWB needs clone mode API check to ensure resource
allocations are correct. But currently during first
CWB commit, clone mode API is returning false as
sde encoder master is NULL at the point where
LM/PP reservation is done. Hence, use a API for CWB
clone mode check which doesn't check sde encoder
master structure instead gets information from phys
encoder structure.

Change-Id: I7bf3f3cb8b3cc23f6d92bb6a9d98a3f35bcb840e
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Raviteja Tamatam <travitej@codeaurora.org>