rtw88: report tx rate to mac80211 stack

Whenever the firmware increases/decreases the bit rate used
to transmit to a peer, it sends an RA report through C2H to
driver. Driver can then record the bit rate in the peer's
struct rtw_sta_info, and report to mac80211 when it asks us
for the statistics of the sta by ieee80211_ops::sta_statistics

Signed-off-by: Tzu-En Huang <tehuang@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>