rtw88: fix rate mask for 1SS chip

The rate mask is used to tell firmware the supported rate depends on
negotiation. We loop 2 times for all VHT/HT 2SS rate mask first, and then
only keep the part according to chip's NSS.

This commit fixes the logic error of '&' operations for VHT/HT rate, and
we should run this logic before adding legacy rate.

To access HT MCS map, index 0/1 represent MCS 0-7/8-15 respectively. Use
NL80211_BAND_xxx is incorrect, so fix it as well.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Reviewed-by: Chris Chiu <chiu@endlessm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>