Make conv2d nnapi converter accept flexible batch (#61021)
Summary:
Same as title
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61021
Test Plan: pytest test/test_nnapi.py::TestNNAPI
Reviewed By: anshuljain1
Differential Revision: D29480746
fbshipit-source-id: 7217c8f3a811db8c3c373f3e7ca31caf9502ef22
