[ALSA] dbri: more cleanups

This patch:
- removes redundant constant suffices
- removes redundant parentheses
- removes redundant curly brackets
- removes check if a spinlock is locked inside method which is
  only called with the spinlock locked
- moves few functions to the __init section
- removes line which appears twice after the previous patch
- minor comments improvements

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>