ath10k: send (re)assoc peer command when NSS changed

Assoc peer command contain information about NSS.
When we will get IEEE80211_RC_NSS_CHANGED we should
also send (re) assoc peer command to be sure firmware
will know about it and RC will work correctly.

This was found during code review.

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>