[Intel-gfx] Atomic and two-level watermark support for VLV and CHV

[chix.ding at intel.com]

[RFC 1/5] Remove unused parameters from intel_plane_wm_parameters
[RFC 2/5] Rename skl_plane_id to wm_plane_id
[RFC 3/5] Move fifo_size from intel_plane_wm_parameters to
[RFC 4/5] Add optimal field in intel_crtc_wm_state for VLV 
[RFC 5/5] Add intermediate field in intel_crtc_wm_state and handlers