ALSA: lx_core: Switch to using BIT macro

Move to using the BIT macro for a few defines. It also allows to discard the
french comment that was saying exactly what the BIT macro is now pointing out.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>