sound: Fix oss_audioinfo's card_number, port_number and legacy_device

Although the docs advise against using them, it doesn't hurt to fill
them out correctly.

Sponsored by: The FreeBSD Foundation
MFC after: 1 day
Reviewed by: dev_submerge.ch, markj
Differential Revision: https://reviews.freebsd.org/D45604

(cherry picked from commit 0f878cdfc5a46cc0dc198e12758f12558dfb1bf6)