gralloc 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

Bug: 33844934
Change-Id: I65d9d283fe7b72ddb286ff41bd23ca33345d466c
diff --git a/libs/ui/GrallocAllocator.cpp b/libs/ui/GrallocAllocator.cpp
index ca67990..8799fab 100644
--- a/libs/ui/GrallocAllocator.cpp
+++ b/libs/ui/GrallocAllocator.cpp
@@ -28,7 +28,7 @@
 
 Allocator::Allocator()
 {
-    mAllocator = IAllocator::getService("gralloc");
+    mAllocator = IAllocator::getService();
     if (mAllocator != nullptr) {
         mAllocator->createClient(
                 [&](const auto& tmpError, const auto& tmpClient) {