wifi HAL uses "default" service name

The getService() and registerAsService() methods of interface objects
now have default parameters of "default" for the service name. HALs
will not have to use any service name unless they want to register
more than one service.

Test: builds; verify HAL still works

In support of b/33844934

Change-Id: Ia086509b3433976524bc4a0ac4b24385840ce565
diff --git a/wifi/1.0/default/service.cpp b/wifi/1.0/default/service.cpp
index 40e8b12..96d5c6f 100644
--- a/wifi/1.0/default/service.cpp
+++ b/wifi/1.0/default/service.cpp
@@ -34,7 +34,7 @@
   // Setup hwbinder service
   android::sp<android::hardware::wifi::V1_0::IWifi> service =
       new android::hardware::wifi::V1_0::implementation::Wifi();
-  CHECK_EQ(service->registerAsService("wifi"), android::NO_ERROR)
+  CHECK_EQ(service->registerAsService(), android::NO_ERROR)
       << "Failed to register wifi HAL";
 
   joinRpcThreadpool();