[mlir][sparse] fix typos

[aartbik]

Summary

Perhaps one of these days I will actually learn how to spell opaque....

mlir/lib/ExecutionEngine/SparseUtils.cpp

 //     tensors. These methods should be used exclusively by MLIR
 //     compiler-generated code.
 //
 // (II) Methods that accept C-style data structures to interact with sparse
 //      tensors. These methods can be used by any external runtime that wants
 //      to interact with MLIR compiler-generated code.
 //
 // In both cases (I) and (II), the SparseTensorStorage format is externally
-// only visible as an opague pointer.
+// only visible as an opaque pointer.
 //
 //===----------------------------------------------------------------------===//
 
 namespace {
 
 /// A sparse tensor element in coordinate scheme (value and indices).
 /// For example, a rank-1 vector element would look like
 ///   ({i}, a[i])
SparseTensorCOO<double> *tensor = SparseTensorCOO<double>::newSparseTensorCOO(
       rank, shape, perm.data(), nse);
   std::vector<uint64_t> idx(rank);
   for (uint64_t i = 0, base = 0; i < nse; i++) {
     for (uint64_t j = 0; j < rank; j++)
       idx[j] = indices[base + j];
     tensor->add(idx, values[i]);
     base += rank;
   }
-  // Return sparse tensor storage format as opague pointer.
+  // Return sparse tensor storage format as opaque pointer.
   return SparseTensorStorage<uint64_t, uint64_t, double>::newSparseTensor(
       tensor, sparse.data(), perm.data());
 }
 
 } // extern "C"
 
 #endif // MLIR_CRUNNERUTILS_DEFINE_FUNCTIONS