audio: Fix alsa settings access
OpenAL application on Debian Buster produces deny message:
type=AVC msg=audit(1547295526.633:732): apparmor="DENIED"
operation="open" profile="supertuxkart" name="/etc/alsa/conf.d/"
pid=13963 comm="supertuxkart" reque
sted_mask="r" denied_mask="r" fsuid=1000 ouid=0
Add file rule to allow reading Alsa configuration files.