mac80211_hwsim: Update timestamp in Probe Response frames

Previously, this was done only for Beacon frames, but similar timestamp
update is needed for Probe Response frames to make these more accurately
match the real IEEE 802.11 behavior. Previously, all zeros timestamp was
sent in Probe Response frames.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>