hwc2: Clean up display slot handling.

-- Deprecate SetDisplayIndex api.
-- Query for max display supported displays per type.
-- Create display_map corresponding to capabilities.
-- Fail creation of any display if free slot isn't available.

Change-Id: Ic22f5695e7425a68ca7d4c85f0b85703055abe63
CRs-fixed: 2429625
4 files changed