mac80211: minor cleanup

we would have bailed out if 'ifibss->fixed_channel'
is valid i.e. we had used 'fixed-freq' parameter in iw ibss
join command. this is with the state 'IEEE80211_IBSS_MLME_JOINED'
so no need to check for it

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>