qcacld-3.0: clear pmkid cache when ap off

In AP side power off/on case, AP security has been cleanup.
The STA side might still cache PMK ID in driver and it will always
use PMK cache to connect to AP and get continuously connect failure
in SAE security. This function is to detect AP off based on FW
reported BMISS event. Meanwhile judge FW reported last RSSI > roaming
Low rssi and not less than 20db of host cached RSSI to avoid
some false alarm such as normal DUT roll in/out roaming.

Change-Id: I5d8ec9e9d4f8a44178b113d370799fe2bc0373fb
CRs-Fixed: 2841481

components/mlme/dispatcher/inc/wlan_mlme_public_struct.h

@@ -86,6 +86,13 @@
 #define CFG_VALID_CHANNEL_LIST_STRING_LEN (CFG_VALID_CHANNEL_LIST_LEN * 4)
 
 #define DEFAULT_ROAM_TRIGGER_BITMAP 0xFFFFFFFF
+
+/**
+ * detect AP off based FW reported last RSSI > roaming Low rssi
+ * and not less than 20db of host cached RSSI
+ */
+#define AP_OFF_RSSI_OFFSET 20
+
 /**
  * struct mlme_cfg_str - generic structure for all mlme CFG string items
  *