qcacmn: Re initialize default SAP mandatory channel list

Re initialize default SAP mandatory channel list as part of the
start bss. Without this change the 5GHz channels which were
added as part of previous start bss are valid for the current
start bss operation.

Change-Id: Id234b413bbddb05efd3af8c3349271bf93a0a3bd
CRs-Fixed: 2300501

umac/cmn_services/policy_mgr/src/wlan_policy_mgr_core.c

@@ -2981,6 +2981,8 @@ void  policy_mgr_init_sap_mandatory_2g_chan(struct wlan_objmgr_psoc *psoc)
 		policy_mgr_err("Error in getting valid channels");
 		return;
 	}
+	pm_ctx->sap_mandatory_channels_len = 0;
+
 	for (i = 0; i < len; i++) {
 		if (WLAN_REG_IS_24GHZ_CH(chan_list[i])) {
 			policy_mgr_debug("Add chan %hu to mandatory list",