mac80211-hwsim: Rename CREATE and DESTROY radio to NEW and DEL radio

Using the name HWSIM_CMD_NEW_RADIO and HWSIM_CMD_DEL_RADIO is more
fitting on how other pieces of the wireless system work.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>