its-g5: Remove useless chan. check since it is already in ieee80211_vif_use_channel()

Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
its-g5: We definitely do not need to be promiscuous

Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
its-g5: Fix comments

Signed-off-by: Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>