ath10k: maintain peer_id for each sta and vif

The 10.4.3 firmware with congestion control
guarantees that each peer has only a single
peer_id mapping.

The 1:1 mapping isn't the case for older firmwares
(e.g. 10.4.1, 10.2, 10.1) but it should not
matter. This 1:1 mapping is going to be only used
by future code which inherently (flow-wise) is for
10.4.3.

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