fix data type logging (#53162)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53162
it is possible there are multiple data types in mixed precision training, so log data types as a list of data type names.
ghstack-source-id: 123452626
Test Plan: unit test
Reviewed By: SciPioneer
Differential Revision: D26769256
fbshipit-source-id: 8f7d73821e89864fedbbce723f301fe8fbad5685
