[ALSA] emu10k1 - Clean up p16v code

Modules: EMU10K1/EMU10K2 driver

Clean up and optimize the codes in p16v.c

- Add proper __devinit* tags
- Reduce unnecessary functions using a closure
- Fix whitespaces
- Rename 'Unknown' to 'Side' controls

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