ath10k: fix SMPS support

Firmware ignores SMPS flags in peer assoc command.

For SMPS to work it is necessary to set peer
parameter after peer assoc command so that tx
chainmask is setup properly.

This should fix packet loss and improve throughput
with stations that have SMPS enabled upon
association.

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