mac80211_hwsim: Add tsf to beacons, probe responses and radiotap header.
Generate a tsf from internal kernel clock. Prepare the path for having
different tsf offsets on each phy. This will be useful for testing
mesh synchronization algorithms.
Signed-off-by: Javier Cardona <javier@cozybit.com> Reviewed-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>