wifi: mac80211: don't send an unused argument to ieee80211_check_combinations

wifi: mac80211: don't send an unused argument to ieee80211_check_combinations

When ieee80211_check_combinations is called with NULL as the chandef,
the chanmode argument is not relevant. Send a don't care (0) instead.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260111192411.9aa743647b43.I407b3d878d94464ce01e25f16c6e2b687bcd8b5a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>