ALSA: hda - Fix possible races in HDMI driver

Some per_pin fields and ELD contents might be changed dynamically in
multiple ways where the concurrent accesses are still opened in the
current code.  This patch fixes such possible races by using eld->lock
in appropriate places.

Reported-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Takashi Iwai <tiwai@suse.de>