[mlir][SPIRV] Fix blocks nested too deeply error.

Issue arises due to a giant if/else if/else/... construct. Changing
them to just ifs.

Differential Revision: https://reviews.llvm.org/D80245

Author: MaheshRavishankar

mlir/tools/mlir-tblgen/SPIRVUtilsGen.cpp

@@ -707,7 +707,7 @@ static void emitSerializationFunction(const Record *attrClass,
 static void initDispatchSerializationFn(StringRef opVar, raw_ostream &os) {
   os << formatv(
       "LogicalResult Serializer::dispatchToAutogenSerialization(Operation "
-      "*{0}) {{\n ",
+      "*{0}) {{\n",
       opVar);
 }
 
@@ -721,18 +721,15 @@ static void emitSerializationDispatch(const Operator &op, StringRef tabs,
   os << tabs
      << formatv("  return processOp(cast<{0}>({1}));\n",
                 op.getQualCppClassName(), opVar);
-  os << tabs << "} else";
+  os << tabs << "}\n";
 }
 
 /// Generates the epilogue for the function that dispatches the serialization of
 /// the operation.
 static void finalizeDispatchSerializationFn(StringRef opVar, raw_ostream &os) {
-  os << " {\n";
   os << formatv(
-      "    return {0}->emitError(\"unhandled operation serialization\");\n",
+      "  return {0}->emitError(\"unhandled operation serialization\");\n",
       opVar);
-  os << "  }\n";
-  os << "  return success();\n";
   os << "}\n\n";
 }