When initializing rates selections starting indexes upon stats update,
the minstrel_sta->max_* rates should be 'group * MCS_GROUP_RATES + i'
not 'i'. This affects settings where one of the peers does not support
any of the rates of the group 0 (i.e. when ht_cap.mcs.rx_mask[0] == 0).
Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com> Acked-by: Felix Fietkau <nbd@openwrt.org> Signed-off-by: Johannes Berg <johannes.berg@intel.com>