iwlagn: fix FH error

# iw wlan0 interface add moni0 type monitor flags control
# ip link set moni0 up

causes a continuous spew of FH_ERROR from the
device. Fix this by not setting the CTL2HOST
filter by itself -- CTL + promisc works fine.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>