hostapd(hidl): Add HIDL interface skeletal code

Adding support for HIDL IPC in hostapd. This CL only adds the skeletal
framework for supporting HIDL interface implementation.

There is also a change in the hostapd.h to fix a C++ compilation error.

Bug: 36646171
Test: Compiles with CONFIG_CTRL_IFACE_HIDL=y in android.config
Change-Id: I4a7047a56f8e9be1ed51f2315df707ef5daddc11
diff --git a/src/ap/hostapd.h b/src/ap/hostapd.h
index f77e6ec..d7c6720 100644
--- a/src/ap/hostapd.h
+++ b/src/ap/hostapd.h
@@ -372,6 +372,16 @@
 #endif /* CONFIG_TAXONOMY */
 };
 
+enum hostapd_iface_state {
+	HAPD_IFACE_UNINITIALIZED,
+	HAPD_IFACE_DISABLED,
+	HAPD_IFACE_COUNTRY_UPDATE,
+	HAPD_IFACE_ACS,
+	HAPD_IFACE_HT_SCAN,
+	HAPD_IFACE_DFS,
+	HAPD_IFACE_ENABLED
+};
+
 /**
  * struct hostapd_iface - hostapd per-interface data structure
  */
@@ -382,16 +392,7 @@
 	struct hostapd_config *conf;
 	char phy[16]; /* Name of the PHY (radio) */
 
-	enum hostapd_iface_state {
-		HAPD_IFACE_UNINITIALIZED,
-		HAPD_IFACE_DISABLED,
-		HAPD_IFACE_COUNTRY_UPDATE,
-		HAPD_IFACE_ACS,
-		HAPD_IFACE_HT_SCAN,
-		HAPD_IFACE_DFS,
-		HAPD_IFACE_ENABLED
-	} state;
-
+        enum hostapd_iface_state state;
 #ifdef CONFIG_MESH
 	struct mesh_conf *mconf;
 #endif /* CONFIG_MESH */