drm/i915: Improve kernel-doc for i915_audio_component struct

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1444987464-8657-1-git-send-email-david.henningsson@canonical.com


Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>