ALSA: hda - Fix inconsistent monitor_present state until repoll

While the previous commit fixed the missing monitor_present flag
update, it may be still in an inconsistent state while the driver
repolls: the flag itself is updated, but the eld_valid flag and the
contents don't follow until the repoll finishes (and may be repeated
for a few times).

The basic problem is that pin_eld->monitor_present is updated in the
caller side.  This should have been updated only in update_eld().  So,
the proper fix is to avoid accessing pin_eld but only spec->temp_eld.

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