kernel -- ffs: Softdep lock and assorted fixes

kernel -- ffs: Softdep lock and assorted fixes

* Remove interlocked_sleep; we can just use lksleep directly

* sema_get no longer eats the interlock passed in; all of its
  callers were retaking the lock eventually or immediately.

* softdep was setting up a callout to wake itself in request_cleanup.
  Switch to directly using timeout in lksleep for this purpose.

* Do not access inodedep structure outside of softdep lock in
  softdep_update_inodeblock for buffer field.

* Remove prio field from semaphores; they were unused and the DFly
  tsleep routines do not respect priority anyway.

* Do not release softdep lock before panic()ing