wifi: nl80211: refactor nl80211_parse_chandef

wifi: nl80211: refactor nl80211_parse_chandef

In order to be able to use this function also for nested attributes,
change this function to receive a pointer to extack and to the
attributes array, instead of receiving the info and extracting them out
of it.
While at it, use NL_SET_ERR_MSG_ATTR with the frequency of the chandef.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260219114327.2b994566a63b.I6c2b6f4c7e2e09f4c47285ca4ac8a37b20700e19@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>