[NNC] Don't attempt to refactor conditional scalars (#44223)
Summary:
Fixes a bug in the NNC registerizer for Cuda where it would hoist reads out of a conditional context when trying to cache them. As a quick fix, prevent scalar replacement if a usage is within a condition.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44223
Reviewed By: gchanan
Differential Revision: D23551247
Pulled By: nickgg
fbshipit-source-id: 17a7bf2be4c8c3dd8a9ab7997dce9aea200c3685
