ath10k: implement fw stats for wmi-tlv

This processes and pushes fw stats to the debug
module (if enabled).

Changing the generic ath10k_wmi_requests_stats()
call to use more stat bits has no effect on older
firmware binaries.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>