Add getInstance call to LazyServiceRegistrar

This is the first step in converting LazyServiceRegistrar to a
singleton. A later CL will make the constructor private.

Test: lshal
Bug: 139376253
Change-Id: I07f65327737b94656a91b2a9dcc67a28075b4406
diff --git a/transport/include/hidl/HidlLazyUtils.h b/transport/include/hidl/HidlLazyUtils.h
index 2205daa..257de98 100644
--- a/transport/include/hidl/HidlLazyUtils.h
+++ b/transport/include/hidl/HidlLazyUtils.h
@@ -29,12 +29,13 @@
 /** Exits when all HALs registered through this object have 0 clients */
 class LazyServiceRegistrar {
    public:
-    LazyServiceRegistrar();
-    status_t registerService(const sp<::android::hidl::base::V1_0::IBase>& service,
-                             const std::string& name = "default");
+     LazyServiceRegistrar();
+     static LazyServiceRegistrar& getInstance();
+     status_t registerService(const sp<::android::hidl::base::V1_0::IBase>& service,
+                              const std::string& name = "default");
 
    private:
-    std::shared_ptr<details::LazyServiceRegistrarImpl> mImpl;
+     std::shared_ptr<details::LazyServiceRegistrarImpl> mImpl;
 };
 
 }  // namespace hardware