[MAC80211]: remove unused ioctls (2)

The ioctls

 * PRISM2_PARAM_STA_ANTENNA_SEL
 * PRISM2_PARAM_TX_POWER_REDUCTION
 * PRISM2_PARAM_DEFAULT_WEP_ONLY

are not used by hostapd or wpa_supplicant.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>