[MAC80211]: remove IEEE80211_HW_HOST_GEN_BEACON flag

The flag is never checked because drivers can simply call
ieee80211_beacon_get() regardless of setting this flag.

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>