msm: mdss: Decimation and BWC cannot be enabled together

Hardware cannot support decimation and bwc together.
The use case should be failed.

Change-Id: Ic7547340eb08d542a296aa9cfdd150e7eb0bea4b
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@quicinc.com>