Fix out-of-bounds access for caching allocator calls (#46439)
Summary:
In assertValidDevice() compare device index to `caching_allocator.device_allocator` rather than to `device_no`
Fixes potential crashes when caching allocator is accessed before being initialized, for example by calling something like:
`python -c "import torch;print(torch.cuda.memory_stats(0))"`
Fixes https://github.com/pytorch/pytorch/issues/46437
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46439
Reviewed By: ngimel
Differential Revision: D24350717
Pulled By: malfet
fbshipit-source-id: 714e6e74f7c2367a9830b0292478270192f07a7f
