fix anti-pattern for cudagraph (#2619)
Summary:
Previously, `self.create_grids((nx, ny), p.device)` is run sometimes, leading to cudagraph error "accessing tensor output of CUDAGraphs that has been overwritten by a subsequent run". This pr fixes the anti-pattern to always run `create_grids`.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/2619
Reviewed By: ydwu4
Differential Revision: D75250139
Pulled By: BoyuanFeng
fbshipit-source-id: 7aa4e5c16031f5e85b8493f9ee0e2e25f7af8ca8
