ath10k: fix tx legacy rate reporting

Tx legacy rate is reported 10 fold, as below

iw dev wlan#N station dump | grep "tx bitrate"
        tx bitrate:     240.0 MBit/s

This is because by mistake we multiply by the hardware reported
rate twice by 10, fix this.

Fixes: cec17c38 ("ath10k: add per peer htt tx stats support for 10.4")
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>