ALSA: cs5535audio: turn off PCM properly if closing the audio device

As per <http://dev.laptop.org/ticket/1420

>, we need to properly turn off
the PCM if we're closing the device in order to save power.  This also
causes the MIC led to turn off properly.

Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Signed-off-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>