sdm: HDMI as primary and headless display support

Add support for a NULL display that closes all fences and allows
SurfaceFlinger to work without a display connected.

Also add support for ability to connect/disconnect and suspend/resume
HDMI primary display by using NULL display.

CRs-Fixed: 814136
Change-Id: I6ec1149de2a6e5e34aeae0a10e9bc226edd4aa04
24 files changed