Fix RNN modules with inputs shapes containing-0 in CUDA (#71696)
Summary:
We found a discrepancy between cpu & CUDA when using RNN modules where input shapes containing 0s would cause an invalid configuration argument error in CUDA (kernel grid size is 0), while returning a valid tensor in CPU cases.
A reproducer:
```
import torch
x = torch.zeros((5, 0, 3)).cuda()
gru = torch.nn.GRU(input_size=3, hidden_size=4).to("cuda")
gru(x)
```
Run with `CUDA_LAUNCH_BLOCKING=1` set.
cc ngimel albanD
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71696
Reviewed By: mikaylagawarecki
Differential Revision: D33743674
Pulled By: ngimel
fbshipit-source-id: e9334175d10969fdf1f9c63985910d944bbd26e7
(cherry picked from commit 70838ba69bbfd1b39f6c208f9dbefaad3f11d47e)
