ath6kl: Fix target minimum length requirement for WMI_SEND_PROBE_RESPONSE_CMDID

The firmware expects the minimum length of
WMI_SEND_PROBE_RESPONSE_CMDID to be 13. However, when the device is a
P2P GO and it needs to send a probe response to a non-P2P client,
there are no P2P IEs to be added, and therefore the length of the WMI
command is 12. This command gets rejected by the firmware. To fix
this, add an extra byte to satisfy the minimum length requirement.

Signed-off-by: Aarthi Thiruvengadam <athiruve@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>