Fix warning couldn't find split args (#102561)
Summary:
Fixes #102416 [WARNING] couldn't find split args
In case `dim=` kwarg is absent is absent, we can default it to 0. Even after this, probably okay to make this an INFO rather than a WARNING
Test Plan: run torchbench
Differential Revision: D46292754
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102561
Approved by: https://github.com/jansel
