qcacld-3.0: Fix deadlock when SAP interface down during pre_cac failure

While pre cac is in progress and if the SAP is stopped from UI, It may
lead to dead-lock due to rtnl lock. This is because, stopping SAP will
trigger the stop_ap first and then hostapd_stop. Stop_ap will schedule
a work to handle pre_cac failure (Thread1). hostapd_stop will be
triggered in parallel (Thread2). This will result in a below dead-lock
scenario.
   Thread1: Waiting to acquire rtnl_lock to unregister pre_cac adapter.
   Thread2: Acquired the rtnl_lock and waiting for Thread1 to complete

To resolve this dead-lock, unregister pre_cac_adapter during
hostapd_stop without requesting for rtnl_lock.

Change-Id: I222df9ee0d75b16f79c28b7cdd86369c340a15c2
CRs-Fixed: 2832256

core/sap/inc/sap_api.h

@@ -67,6 +67,8 @@ extern "C" {
 #define SAP_DEFAULT_5GHZ_CHANNEL      (40)
 #define SAP_CHANNEL_NOT_SELECTED (0)
 
+#define SAP_PRE_CAC_IFNAME "precac"
+
 /*--------------------------------------------------------------------------
  * reasonCode taken from 802.11 standard.
  * ------------------------------------------------------------------------*/
@@ -832,6 +834,7 @@ QDF_STATUS wlan_sap_update_next_channel(struct sap_context *sap_ctx,
 					uint8_t channel,
 					enum phy_ch_width chan_bw);
 
+#ifdef FEATURE_SAP_COND_CHAN_SWITCH
 /**
  * wlan_sap_set_pre_cac_status() - Set the pre cac status
  * @sap_ctx: SAP context
@@ -855,6 +858,20 @@ QDF_STATUS wlan_sap_set_pre_cac_status(struct sap_context *sap_ctx,
  */
 QDF_STATUS wlan_sap_set_chan_before_pre_cac(struct sap_context *sap_ctx,
 					    uint8_t chan_before_pre_cac);
+#else
+static inline QDF_STATUS
+wlan_sap_set_pre_cac_status(struct sap_context *sap_ctx, bool status)
+{
+	return QDF_STATUS_SUCCESS;
+}
+
+static inline QDF_STATUS
+wlan_sap_set_chan_before_pre_cac(struct sap_context *sap_ctx,
+				 uint8_t chan_before_pre_cac)
+{
+	return QDF_STATUS_SUCCESS;
+}
+#endif
 
 /**
  * wlan_sap_set_pre_cac_complete_status() - Sets pre cac complete status