wifi: mac80211_hwsim: rename and switch simulation time to boottime

wifi: mac80211_hwsim: rename and switch simulation time to boottime

The mac80211_hwsim base time for the simulation of the TSF was based on
the real time of the system. This clock is subject to unexpected
changes. Switch it to use boottime which is always monotonic and also
continues to run through times where the system is suspended.

Also change the function name from tsf_raw to sim_tsf to better
differentiate between the TSF of the mac and the TSF base of the
simulation.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260504101829.2a64333111ff.I2ef047f3cdd6dc52af4bb7bf747368fb78014f18@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>