TXOP (also known as Channel Occupancy Time) is u16 and should be
added using nla_put_u16 instead of u8, fix that.

Fixes: 50f32718 ("nl80211: Add wmm rule attribute to NL80211_CMD_GET_WIPHY dump command")
Signed-off-by: NHaim Dreyfuss <haim.dreyfuss@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>