IUsb 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: pass

Bug: 33844934
Change-Id: Ic04a7570c090d9d0a83bac1ec3f6d5ffe19e8923
diff --git a/usb/1.0/default/service.cpp b/usb/1.0/default/service.cpp
index b4db241..4605a4c 100644
--- a/usb/1.0/default/service.cpp
+++ b/usb/1.0/default/service.cpp
@@ -28,12 +28,11 @@
 using android::hardware::usb::V1_0::implementation::Usb;
 
 int main() {
-    const char instance[] = "usb_hal";
 
     android::sp<IUsb> service = new Usb();
 
     configureRpcThreadpool(1, true /*callerWillJoin*/);
-    service->registerAsService(instance);
+    service->registerAsService();
 
     ALOGI("USB HAL Ready.");
     joinRpcThreadpool();