[MLIR] NFC. Remove anti-patterns given the default null init for Value (#99457)

Summary:
Remove anti-patterns given the default null init for Value. Drop some
extra includes while on this file. NFC.

Co-authored-by: GitHub runner <[email protected]>

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Differential Revision: https://phabricator.intern.facebook.com/D60250846

Author: bondhugula

mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp

@@ -12,10 +12,8 @@
 
 #include "mlir/Dialect/Affine/LoopUtils.h"
 #include "mlir/Analysis/SliceAnalysis.h"
-#include "mlir/Dialect/Affine/Analysis/AffineAnalysis.h"
 #include "mlir/Dialect/Affine/Analysis/LoopAnalysis.h"
 #include "mlir/Dialect/Affine/Analysis/Utils.h"
-#include "mlir/Dialect/Affine/IR/AffineOps.h"
 #include "mlir/Dialect/Affine/IR/AffineValueMap.h"
 #include "mlir/Dialect/Affine/Utils.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
@@ -2082,8 +2080,8 @@ static LogicalResult generateCopy(
 
   auto numElementsSSA = top.create<arith::ConstantIndexOp>(loc, *numElements);
 
-  Value dmaStride = nullptr;
-  Value numEltPerDmaStride = nullptr;
+  Value dmaStride;
+  Value numEltPerDmaStride;
   if (copyOptions.generateDma) {
     SmallVector<StrideInfo, 4> dmaStrideInfos;
     getMultiLevelStrides(region, fastBufferShape, &dmaStrideInfos);