ALSA: hda - hdmi: Protect ELD buffer

ALSA: hda - hdmi: Protect ELD buffer

Because the eld buffer can be simultaneously accessed from both
workqueue context (updating) and process context (kcontrol read),
we need to protect it with a mutex to guarantee consistency.

To avoid holding the mutex while reading the ELD info from the
codec, we introduce a temporary eld buffer.

Signed-off-by: David Henningsson <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>