Run deepwalk examples with ogbn data

## 🚀 Feature

The [deepwalk example]( https://github.com/dmlc/dgl/tree/master/examples/pytorch/ogb/deepwalkhttps://github.com/dmlc/dgl/tree/master/examples/pytorch/ogb/deepwalk) currently only supports [ogbl dataset](https://ogb.stanford.edu/docs/nodeprop/). It should be great to add support of [ogbn dataset](https://ogb.stanford.edu/docs/nodeprop/).

## Motivation
When comparing the implementation from DGL to other libraries, deepwalk algorithm is often a starting point so both ogbn and ogbl should be included into the dataset if a comprehensive test is expected.