target: support HDMI as primary display interface

Support HDMI as primary interface on APQ8084/MSM8974 for
debugging, testing and other purposes. Do not initialize
other interfaces when HDMI is selected as primary interface.

Use below commands to make hdmi as primary, the settings are
persistent across power cycles:

* Reboot the device into fastboot mode
* fastboot oem select-display-panel hdmi
* fastboot reboot-bootloader
* Reboot device

Change-Id: Iefe53528c3a2be82b6e43184549e4530b9c2570a
6 files changed