mac80211_hwsim: check ATTR_FREQ for wmediumd (netlink) packets

If a packet is received from netlink with the frequency value set it is
checked against the current radio's frequency and discarded if different.
The frequency is also checked against data2->tmp_chan to support the "hw"
off-channel/scan case.

Signed-off-by: Adam Welle <arwelle@cert.org>
[allow both simultaneously, add locking]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>