ALSA: hda - Fix the logic to detect VIA analog low-current mode

The analog low-current mode must be enabled when the no stream is
running but the current detection checks it in a wrong way.

Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=741128



Cc: <stable@kernel.org> [v3.1+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>