mac80211_hwsim: fill boottime_ns in netlink RX path

Give a proper boottime_ns value for netlink RX to avoid scan
issues here.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20190729160605.1074-1-johannes@sipsolutions.net


Signed-off-by: Johannes Berg <johannes.berg@intel.com>