[Intel-gfx] i915 Displayport Compliance Testing

[Todd Previte]

This patch set adds the foundational support for Displayport compliance testing in the
i915 driver. It implements the framework for automated test support that preclude the
need (most) for operator input during testing. Tests for AUX transactions, EDID reads
and basic link training have also been included, along with any support and utility
functions required. Some changes have also been made to existing code to accommodate 
compliance testing.