sound: Create all device nodes with GID_AUDIO

Commit 6024e3f99a ("Add audio group") introduced GID_AUDIO, initially
for virtual_oss(8) loopback devices. Now make all of them with
GID_AUDIO.

Relnotes:	yes
Sponsored by:	The FreeBSD Foundation
Reviewed by:	emaste
Pull-Request:	https://ron-dev.freebsd.org/FreeBSD/src/pulls/35

UPDATING

@@ -27,6 +27,9 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 16.x IS SLOW:
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20260521:
+	Audio devices are now created with GID 43 / audio. You will need to add
+	users who need access to audio devices to this group.
 20260512:
 	"bsdinstall script" will now do a pkgbase installation by default.  To
 	revert to the legacy distset installation, set "DISTRIBUTIONS" in