Add get_eld audio component for i915/HD-audio Here are the patchset to add get_eld op to audio component for communicating more directly between i915 and HD-audio. Currently, the HDMI/DP audio status and ELD are notified and obtained via the hardware-level communication over HD-audio unsolicited event and verbs although the graphics driver holds the exactly same information. As we already have a notification via audio component, this is another step forward; namely, the audio driver may fetch directly the audio status and ELD via the new component op. The commits are based on Dave's latest drm-next branch.