wifi: cfg80211: expose cfg80211_iter_rnr() to drivers

In mac80211 we'll need to look at reduced neighbor report
entries for channel switch purposes, so export the iteration
function to make that simpler.

Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240228095718.0954809964ef.I53e95c017aa71f14e8d1057afbbc75982ddb43df@changeid


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