wifi: mac80211: Use active_links instead of valid_links in Tx

Fix few places on the Tx path where the valid_links were used instead
of active links.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230608163202.e24832691fc8.I9ac10dc246d7798a8d26b1a94933df5668df63fc@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>