dinput: Remove superfluous cast to self.

dlls/dinput/dinput.c

@@ -944,7 +944,7 @@ HRESULT WINAPI DECLSPEC_HOTPATCH DirectInput8Create( HINSTANCE hinst, DWORD vers
 
     if (outer || FAILED(hr = IDirectInput8_Initialize( (IDirectInput8W *)unknown, hinst, version )))
     {
-        IUnknown_Release( (IUnknown *)unknown );
+        IUnknown_Release( unknown );
         *out = NULL;
         return hr;
     }

dlls/dinput/tests/dinput.c

@@ -84,7 +84,7 @@ static HRESULT WINAPI outer_QueryInterface( IUnknown *iface, REFIID iid, void **
 
     if (IsEqualGUID( iid, &IID_IUnknown ))
     {
-        *obj = (IUnknown *)iface;
+        *obj = iface;
         return S_OK;
     }