power 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

Bug: 33844934
Change-Id: I2f296bc40e36082d8889d2796cf839cb41a21fc3

services/core/jni/com_android_server_power_PowerManagerService.cpp

@@ -110,7 +110,7 @@ void android_server_PowerManagerService_userActivity(nsecs_t eventTime, int32_t
 static void nativeInit(JNIEnv* env, jobject obj) {
     gPowerManagerServiceObj = env->NewGlobalRef(obj);
 
-    gPowerHal = IPower::getService("power");
+    gPowerHal = IPower::getService();
     if (gPowerHal == nullptr) {
         ALOGE("Couldn't load PowerHAL module");
     }