ath10k: apply Mesh subtype when Mesh interface created.

QCA988X firmware starting from 10.2.4.70.12-2 has capability to support
Mesh Control Field Present bit in QoS field in native Wi-Fi mode.
Hence apply Mesh subtype according to the WMI service map.

Firmware will allows unicast, broadcast, multicast, and WDS frame
(FromDS = 1 and ToDS = 1) to be received via the interface, once Mesh
subtype is used.

The firmware and this patch together make native Wi-Fi mode comply to
IEEE802.11s Mesh frame in open mode, but the firmware doesn't yet
support secured Mesh mode.

Signed-off-by: Peter Oh <poh@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>