drm/msm/sde: Update cp payload to include pointers to DSPPs

Update sde_hw_cp_cfg to include an array of DSPP pointers associated
with the CRTC. This info will be used to support REG DMA broadcast
feature.

Change-Id: Ie9d7945d9b854c85cc3b81675152a3c4e0b65f42
Signed-off-by: Ping Li <pingli@codeaurora.org>