ath10k: add handler for HTT_T2H_MSG_TYPE_SEC_IND event

Add the handler for HTT_T2H_MSG_TYPE_SEC_IND event from firmware, which stores
PN for replay check implemented in the following patch.

Tested on QCA6174 SDIO with firmware WLAN.RMH.4.4.1-00007-QCARMSWP-1.

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>