mac80211: avoid rate init for S1G band

minstrel_ht is confused by the lack of sband->bitrates,
and S1G will likely require a unique RC algorithm, so
avoid rate init for now if STA is on the S1G band.

Signed-off-by: Thomas Pedersen <thomas@adapt-ip.com>
Link: https://lore.kernel.org/r/20200922022818.15855-13-thomas@adapt-ip.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>