service: Use nested namespace specifiers where applicable

There were a few places where nested namespace specifiers weren't being
used where they could be within the service code. This amends that to
make the namespacing a tiny bit more compact.

src/core/hle/service/y2r_u.h

@@ -16,8 +16,7 @@ namespace Kernel {
 class Event;
 }
 
-namespace Service {
-namespace Y2R {
+namespace Service::Y2R {
 
 enum class InputFormat : u8 {
     /// 8-bit input, with YUV components in separate planes and 4:2:2 subsampling.
@@ -301,5 +300,4 @@ private:
 
 void InstallInterfaces(SM::ServiceManager& service_manager);
 
-} // namespace Y2R
-} // namespace Service
+} // namespace Service::Y2R