ath10k: enable transmit data ack RSSI for QCA9884

For all data packets transmitted, host gets htt tx completion event. Some QCA9984
firmware releases support WMI_SERVICE_TX_DATA_ACK_RSSI, which gives data
ack rssi values to host through htt event of data tx completion. Data ack rssi
values are valid if A0 bit is set in HTT rx message. So enable the feature also
for QCA9884.

Tested HW: QCA9984
Tested FW: 10.4-3.9.0.2-00044

Signed-off-by: Abhishek Ambure <aambure@codeaurora.org>
Signed-off-by: Balaji Pothunoori <bpothuno@codeaurora.org>
[kvalo@codeaurora.org: improve commit log]
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>