cfg80211: fix default HE tx bitrate mask in 2G band

cfg80211: fix default HE tx bitrate mask in 2G band

[ Upstream commit 9df66d5b9f45c39b3925d16e8947cc10009b186d ]

In 2G band, a HE sta can only supports HT and HE, but not supports VHT.
In this case, default HE tx bitrate mask isn't filled, when we use iw to
set bitrates without any parameter.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20210609075944.51130-1-pkshih@realtek.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>