wifi: nl80211: expose can-monitor channel property

wifi: nl80211: expose can-monitor channel property

It may be possible to monitor on disabled channels per the
can-monitor flag, but evidently I forgot to expose that out
to userspace. Fix that.

Fixes: a110a3b79177 ("wifi: cfg80211: optionally support monitor on disabled channels")
Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://msgid.link/20240523120945.9a2c19a51e53.I50fa1b1a18b70f63a5095131ac23dc2e71f3d426@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>