Fix coverity defect : Integer overflowed argument
```
6. overflow_sink: Overflowed or truncated value (or a value computed from an overflowed or truncated value) num_of_interm_tensors - 1U used as critical argument to function. [show details]
_interm_tensors[num_of_interm_tensors - 1].allocator()->allocate();
```
ONE-DCO-1.0-Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>
const size_t num_of_kernels = axis.size();
const size_t num_of_interm_tensors = num_of_kernels - (keep_dims ? 1 : 0);
+ ARM_COMPUTE_ERROR_ON(num_of_kernels < 1);
+
_interm_tensors = support::cpp14::make_unique<CLTensor[]>(num_of_interm_tensors);
_reduce_kernels = support::cpp14::make_unique<CLReduceOperationKernel[]>(num_of_kernels);