[2.0] Tweak the argument order for softmax

[Zha0q1]

length is also an input so changing

@set_module('mxnet.numpy_extension')
def softmax(data, axis=-1, length=None, temperature=None, use_length=False, dtype=None):

to

@set_module('mxnet.numpy_extension')
def softmax(data, length=None, axis=-1, temperature=None, use_length=False, dtype=None):

[mxnet-bot]

Hey @Zha0q1 , Thanks for submitting the PR
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[sandeep-krishnamurthy]

This is a breaking backwards incompatible change. Since, master is still beta, this should be okay; But, please capture this in upcoming release notes.

[Zha0q1]

This is a breaking backwards incompatible change. Since, master is still beta, this should be okay; But, please capture this in upcoming release notes.

Yeah, I have sync'ed with @barry-jin who's tracking these changes ;)