sound: Check sndstat_register return value

[guest-ayrton]

Summary

sndstat_register may return EINVAL if a device is not named "pcm" or "midi".
This commit makes pcm_register bubble up the error to its caller instead of
silently ignoring it and allowing a sound driver to continue initialization.
This should not affect in-tree drivers, but is useful for debugging new ones.

Test Plan

I checked that my out-of-tree virtio sound driver still works in QEMU
https://github.com/ayrtonm/freebsd-src/tree/virtio_snd

[christos]

sndstat_register() always returns 0, so perhaps the change instead should be to make the function void.

[guest-ayrton]

Here's the branch in sndstat_register returning EINVAL
https://cgit.freebsd.org/src/tree/sys/dev/sound/pcm/sndstat.c#n1170

[christos]

In D54337#1241919, @guest-ayrton wrote:

Here's the branch in sndstat_register returning EINVAL
https://cgit.freebsd.org/src/tree/sys/dev/sound/pcm/sndstat.c#n1170

Oh, right. I forgot this because I already have a patch to remove this chunk (D54141). I can convert the function to void there instead.

[guest-ayrton]

Oh nice! I'll drop this change then.