[JIT] Use signed integers in CalculatedNecessaryArgs
x was underflowing:
```
size_t x = ...
while (x >= 0) {
x--;
}
```
Changed the variables to ssize_t.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79331
Approved by: https://github.com/yuhc, https://github.com/tugsbayasgalan
