wpa_supplicant(hidl): Use hidl_return_util in |Supplicant|

Use the new helper functions in all |ISupplicant| methods.

Bug: 32869248
Test: Compiles
Change-Id: I6b2d59518311824ac9884e39f07e3efc57980d67
diff --git a/wpa_supplicant/hidl/supplicant.h b/wpa_supplicant/hidl/supplicant.h
index f4a77d9..673b9f5 100644
--- a/wpa_supplicant/hidl/supplicant.h
+++ b/wpa_supplicant/hidl/supplicant.h
@@ -39,6 +39,7 @@
 public:
 	Supplicant(struct wpa_global* global);
 	~Supplicant() override = default;
+	bool isValid();
 
 	// Hidl methods exposed.
 	Return<void> getInterface(
@@ -55,6 +56,16 @@
 	Return<bool> isDebugShowKeysEnabled() override;
 
 private:
+	// Corresponding worker functions for the HIDL methods.
+	std::pair<SupplicantStatus, sp<ISupplicantIface>> getInterfaceInternal(
+	    const IfaceInfo& iface_info);
+	std::pair<SupplicantStatus, std::vector<ISupplicant::IfaceInfo>>
+	listInterfacesInternal();
+	SupplicantStatus registerCallbackInternal(
+	    const sp<ISupplicantCallback>& callback);
+	SupplicantStatus setDebugParamsInternal(
+	    ISupplicant::DebugLevel level, bool show_timestamp, bool show_keys);
+
 	// Raw pointer to the global structure maintained by the core.
 	struct wpa_global* wpa_global_;
 	// Driver name to be used for creating interfaces.