[model][refactor] remove cuda hard code in models and layers

[MengqingCao]

This pr removes cuda hard code in models and layers, so that they could be easily used by the other devices.

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[jeejeelee]

Thanks for this improvement, LGTM

[MengqingCao]

It seems the inference accuracy is breaked by some commit before this pr. I'm looking into it now.

[MengqingCao]

It seems a little far to find which pr introduced the accuracy problem.
I have rebase the code to 9cdea30, but the acc problem still exists.