rename 'mobile' to 'static_dispatch' (#25695)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25695
Rename codegen variables to better reflect its semantics.
As we are going to change other parts of codegen for mobile build, e.g.
autograd, it would be more clear to use more specific names instead of
calling everything 'mobile'.
Test Plan: - will check CI
Differential Revision: D17202732
Pulled By: ljk53
fbshipit-source-id: b2953c0914f25f9a1de00be89a09a6372cc5b614
