iwlwifi: remove ucode16 option

The ucode16 option is still very much work in
progress, so there's no need to ask any users
about it. Remove the option and code for now,
we'll put it back when it's actually working.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>