ath10k: fix ap u-apsd cmd on qca6174 w/ wmi-tlv

The command was truncated so the parameter value
was seen in fw as 0. This caused U-APSD enabled
stations to be misconfigured and mistreated by AP.

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