wifi: nl80211: fix nl80211_start_radar_detection return value

Since the wiphy_guard changes, rdev_start_radar_detection's return value
in nl80211_start_radar_detection is ignored and we always returned 0.

Fixes: f42d22d3 ("wifi: cfg80211: define and use wiphy guard")
Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
Link: https://patch.msgid.link/20250109161040.325742-1-nico.escande@gmail.com


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