[Triton-MLIR] Fix warnings and variable names (#898)

We have been seeing the following error message for a while:

> NO target: Unable to find target for this triple (no targets are
registered)

Seems that it's not necessary to setup the target triple at that point,
so we can just take it out to get rid of the error message.

Variable names have been changed to the camel style.

lib/Target/LLVMIR/LLVMIRTranslation.cpp

@@ -99,9 +99,6 @@ translateLLVMToLLVMIR(llvm::LLVMContext *llvmContext, mlir::ModuleOp module) {
     return nullptr;
   }
 
-  // Initialize LLVM targets.
-  mlir::ExecutionEngine::setupTargetTriple(llvmModule.get());
-
   auto optPipeline = mlir::makeOptimizingTransformer(
       /*optLevel=*/3, /*sizeLevel=*/0,
       /*targetMachine=*/nullptr);