ALSA: hda - Add comments and descriptions to CA0132 functions

Add comments and descriptions to functions.
Bump dsp_free_ports() to below dsp_allocate_ports_format() to group the
alloc functions together for commenting.
Signed-off-by: Ian Minett <ian_minett@creativelabs.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>