wifi: mac80211_hwsim: add control to skip beacons

wifi: mac80211_hwsim: add control to skip beacons

To test certain beacon loss scenarios it can be useful to
simply not send a couple of beacons. Add a simple debugfs
file (per vif) to skip sending the beacons. They're still
fully prepared etc. so their DTIM count etc. will appear
as if they were simply corrupt over the air or otherwise
not received.

Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://msgid.link/20240129200001.a267383709e6.I36f427d17c3478a7df46e205716f5ebc9b35a918@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>