ALSA: cs46xx: Clean up proc file creations

Again no functional changes, but only code clean up.
Use a standard macro for initializing the procfs entries, also drop
the info entries stored in dsp_spos_instance, as they are removed
recursively by a single snd_info_free_entry() calls.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>