Change `dim` to `axis` for tf.nn.softmax and tf.nn.log_softmax (#12716)

* Change `dim` to `axis` for tf.nn.softmax and tf.nn.log_softmax

This fix tries to address the issue raised in 7391 where
`dim` was not changed to `axis` for tf.nn.softmax and tf.nn.log_softmax.
This is inconsistent with other ops in tensorflow.

This fix adds axis while at the same time keeps dim so that
backward compatibility is maintained.

This fix fixes 7391.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Use `@deprecated_args`

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Update goldens for API compatibility changes

This commit updates goldens:
```
bazel-bin/tensorflow/tools/api/tests/api_compatibility_test \
          --update_goldens True
```

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Change `dim` to `axis` for `tf.nn.l2_normalize`

to address #14191.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Update goldens for API compatibility changes

This commit updates goldens:
```
bazel-bin/tensorflow/tools/api/tests/api_compatibility_test \
          --update_goldens True
```

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Use deprecated_argument_lookup to simplify logic

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>