mac80211: ibss: Fix channel type enum in ieee80211_sta_join_ibss()

cfg80211_chandef_create() expects an 'enum nl80211_channel_type' as
channel type however in ieee80211_sta_join_ibss()
NL80211_CHAN_WIDTH_20_NOHT is passed in two occasions, which is of
the enum type 'nl80211_chan_width'. Change the value to NL80211_CHAN_NO_HT
(20 MHz, non-HT channel) of the channel type enum.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>