keymaster 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: marlin boots

Bug: 33844934
Change-Id: I8ba24cd078dc5d36ecf02ddc0febc745b98d5a95

keystore/keystore_main.cpp

@@ -57,7 +57,7 @@ int main(int argc, char* argv[]) {
         return 1;
     }
 
-    auto dev = android::hardware::keymaster::V3_0::IKeymasterDevice::getService("keymaster");
+    auto dev = android::hardware::keymaster::V3_0::IKeymasterDevice::getService();
     if (dev.get() == nullptr) {
         return -1;
     }