message: Allow index typed memrefs in reshape_memref_cast.
  With the recent change to allow memref of index in MLIR core, we should also
  allow this in the mhlo dialect.
diff: @@ -66,6 +66,8 @@ def LHLO_PredOrIntBuffer : MemRefOf<[HLO_Int, HLO_Pred]>;
  def LHLO_Buffer : MemRefOf<[AnyFloat, AnySignlessInteger, AnyComplex]>;
  +def LHLO_ExtentBuffer : MemRefRankOf<[AnySignlessInteger, Index], [1]>;
  +
  //===----------------------------------------------------------------------===//
  // LMHLO nullary op definitions.
  //===----------------------------------------------------------------------===//
  @@ -467,7 +469,7 @@ def ReshapeMemRefCastOp: Op<LHLO_Dialect, "reshape_memref_cast", [
  let arguments = (ins
  AnyRankedOrUnrankedMemRef:$operand,
  - MemRefRankOf<[AnySignlessInteger], [1]>:$shape
  + LHLO_ExtentBuffer:$shape
  );
  let results = (outs AnyRankedOrUnrankedMemRef:$result);
  