ALSA: compress: Fix kernel doc warnings

Each kernel doc comment expects the definition of the return value and
the summary for each struct / enum in a proper format.  This patch
adds or fixes the missing entries for compress-offload API.

Link: https://lore.kernel.org/r/20220713104759.4365-5-tiwai@suse.de


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