- Add noise floor to stats

- Add noise floor to stats
- Include current tx rate in stats
- Remove stub radar support
- Update ath_hal(4) to 0.9.20.3:
  o  Add support for newer parts that do not require separate keycache
     entries for tx+rx mic keys
  o  No more ds_vdata in tx/rx descriptors
  o  Split h/w tx/rx descriptor from s/w status
  o  As part of the descriptor split change the rate control module API
     so the ath_buf is passed in to the module so it can fetch both
     descriptor and status information as needed
- Replace replace h/w descriptor struct's with proper mask+shift defs for
  ath(4) sample TX rate control algorithm.
- Due to the license change in ah_osdep.[ch] (now dual-BSD/GPL), move them
  out of sys/contrib/dev/ath/dragonfly and put them into sys/dev/ath/ath
- Nuke the local patch for ah_osdep.c, ah_osdep.c can be modified directly.

Obtained-from: FreeBSD (sam@freebsd.org)