sound: Make device cloning work
* Some lockstatus() calls were wrong and needed to be compared
with LK_EXCLUSIVE
* The sound device caches dynamically created devices and tries
to reuse them, but devfs got angry if the clone code passed
it a device which was already in the filesystem namespace. devfs
had to be modified in
2c94b9eeb85c6cfa5ff918aa58ce484b27fc7c91
and
eb1c7cbc9e1052820efc6b0b7a94c40a7d45b329
* The clone code was designed to clone to new unit numbers, not
clone an existing unit into multiple channels