ALSA: hda - Split ELD update code from hdmi_present_sense()

This is a preliminary patch for the later change to support ELD/jack
handling with i915 audio component.  This splits the ELD update code
from hdmi_present_sense() so that it can be called from other places.

Just a code refactoring, no functional change.

Signed-off-by: Takashi Iwai <tiwai@suse.de>