[llvm] [NVPTX] enforce signed 32 bit type for immediate offset (PR #99682)

[Artem Belevich via llvm-commits]

Artem-B wrote:

> The NVPTX ISA states that an immOff must be a signed 32-bit 
...
> we generate invalid PTX when a value is offset by a very large immediate.

So, it's not that we want the offset to always be a 32-bit integer, but rather that we need the value to fit in a 32-bit integer. E.g. it would be fine if someone would pass an `i64 1`. You may want to rephrase the commit message to reflect that.

https://github.com/llvm/llvm-project/pull/99682