MFC (revision 1.6)

MFC (revision 1.6)
Misc. fixups:

- [1] Make the driver friendly towards kernel without PREEMPTION.
  Use msleep(9) instead of simple unlock-check_variable-lock
  mechanisme since the later not really effective in non-preemptible
  kernel (especially during codec detection routine).
- Free most driver resources in a sane manner to avoid possible
  double free and panics especially during device detach and codec
  detection failure.

Approved by:	re (scottl)

[1] http://lists.freebsd.org/pipermail/freebsd-questions/2006-March/116515.html