ath10k: fix get invalid tx rate for Mesh metric

ath10k: fix get invalid tx rate for Mesh metric

ath10k does not provide transmit rate info per MSDU
in tx completion, mark that as -1 so mac80211
will ignore the rates. This fixes mac80211 update Mesh
link metric with invalid transmit rate info.

Tested HW: QCA9984
Tested FW: 10.4-3.9.0.2-00035

Signed-off-by: Hou Bao Hou <houbao@codeaurora.org>
Signed-off-by: Anilkumar Kolli <akolli@codeaurora.org>
Signed-off-by: Miaoqing Pan <miaoqing@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>