mac80211: minstrel_ht: fix max probability rate selection

- do not select rates faster than the max throughput rate if probability is lower
- reset previous rate before sorting again

This ensures that the max prob rate gets set to a more reliable rate

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20210115120242.89616-8-nbd@nbd.name


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