ath10k: update wal_dbg_tx_stats structure with missing parameter.

The filed has been missing (missmatched with FW ABI)
since 999.999.0.629 firmware release.

It's very imporatant to keep these structs up to date with FW,
due to the arithmetic we use while read the fw_stats.

Signed-off-by: Bartosz Markowski <bartosz.markowski@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>