[ALSA] ALS4000 update

Modules: SB drivers,ALS4000 driver

some update for the ALS4000 driver (tested with hardware in my PC):

- use common control names according to ControlNames.txt
- add some controls (Master Mono, 3D control)
- optimize struct snd_card_als4000_t layout (performance/size)
- save some bytes via unified error path
- constify some read-only data
- add ToDo list
- move GPL license text to top
- add comments

Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>