sound: Add min_rate and min_channels safety check in SNDCTL_AUDIOINFO

[christos]

Summary

If the channel list is empty, min_rate and min_channels will be INT_MAX.
Instead, assign them to 0, like we do in sndstat_get_caps().

Sponsored by: The FreeBSD Foundation
MFC after: 2 days

[christos]

@dev_submerge.ch I didn't add the same check in dsp_oss_engineinfo() because it will return EINVAL right away if no channel is found, and even if we find it, I don't think it's possible that caps->fmlist can be empty.