[ALSA] add MAINTAINERS entry for snd-aoa

This adds me into the MAINTAINERS file for the AOA driver.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>