dxdiagn: Remove unneeded casts.

dlls/dxdiagn/container.c

@@ -117,7 +117,7 @@ static HRESULT WINAPI IDxDiagContainerImpl_GetChildContainerInternal(PDXDIAGCONT
   p = This->subContainers;
   while (NULL != p) {
     if (0 == lstrcmpW(p->contName, pwszContainer)) {
-      *ppInstance = (PDXDIAGCONTAINER)p->pCont;
+      *ppInstance = p->pCont;
       return S_OK;
     }
     p = p->next;
@@ -159,7 +159,7 @@ static HRESULT WINAPI IDxDiagContainerImpl_GetChildContainer(PDXDIAGCONTAINER if
 
   hr = IDxDiagContainerImpl_GetChildContainerInternal(pContainer, tmp, ppInstance);
   if (SUCCEEDED(hr)) {
-    IDxDiagContainerImpl_AddRef((PDXDIAGCONTAINER)*ppInstance);
+    IDxDiagContainerImpl_AddRef(*ppInstance);
   }
 
 on_error:

dlls/dxdiagn/provider.c

@@ -112,7 +112,7 @@ static HRESULT WINAPI IDxDiagProviderImpl_GetRootContainer(PDXDIAGPROVIDER iface
     if (FAILED(hr)) {
       return hr;
     }
-    hr = DXDiag_InitRootDXDiagContainer((PDXDIAGCONTAINER)This->pRootContainer);
+    hr = DXDiag_InitRootDXDiagContainer(This->pRootContainer);
   }
   return IDxDiagContainerImpl_QueryInterface((PDXDIAGCONTAINER)This->pRootContainer, &IID_IDxDiagContainer, (void**) ppInstance);
 }