wifi: rtw89: no HTC field if TX rate might fallback to legacy

Packets containing HTC field with legacy rate could be dropped by AP. If
TX rate of report is lower than MCS2, hardware might fall back rate to
legacy. Therefore, add a checking rule to avoid HTC field in this
situation.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220826061011.9037-1-pkshih@realtek.com