Fix copy and paste bug

The implementation of DeepTiledInputPart::tileXSize was copy and pasted from the function above but not changed. This causes it tor return incorrect values.

OpenEXR/IlmImf/ImfDeepTiledInputPart.cpp

@@ -90,7 +90,7 @@ DeepTiledInputPart::isComplete () const
 unsigned int
 DeepTiledInputPart::tileXSize () const
 {
-    return file->isComplete();
+    return file->tileXSize();
 }