[FRONTEND] Add scalar type support for some ops (#661)

This PR adds basic support for scalar-type inputs to some ops (cast and pointer arithmetics) for Triton-MLIR. Also renames getelementptr -> addptr

lib/Dialect/Triton/Transforms/Combine.cpp

@@ -194,7 +194,7 @@ public:
     patterns.add<CombineDotAddFRevPattern>(context);
     // %}
     patterns.add<CombineSelectMaskedLoadPattern>(context);
-    patterns.add<CombineGEPPattern>(context);
+    patterns.add<CombineAddPtrPattern>(context);
     patterns.add<CombineBroadcastConstantPattern>(context);
 
     if (applyPatternsAndFoldGreedily(m, std::move(patterns)).failed())