Revert "mac80211: do not use low data rates for data frames with no ack flag"

This reverts commit d3333223 ("mac80211: do not use low data rates for
data frames with no ack flag").

Returning false early in rate_control_send_low breaks sending broadcast
packets, since rate control will not select a rate for it.

Before re-introducing a fixed version of this patch, we should probably also
make some changes to rate control to be more conservative in selecting rates
for no-ack packets and also prevent using probing rates on them, since we won't
get any feedback.

Fixes: d3333223

 ("mac80211: do not use low data rates for data frames with no ack flag")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20210906083559.9109-1-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>