ALSA: lola - Fix for Lola280 board

- add/fix comments and debug messages
- fix incomplete matrix init
- comment out creation of buggy lola_dest_gain_mixer controls
- minor optimisations

Signed-off-by: Markus Bollinger <bollinger@digigram.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>