[clang] [llvm] [Hexagon] Set `hexagon-small-data-threshold` to zero by default (PR #187344)

[Brian Cain via cfe-commits]

androm3da wrote:

> I'm going to defer to @aankit-ca though I suppose Ankit won't have enough history/context to know why it was chosen the way it was?
> 
> I would hope that either @SundeepKushwaha or @quic-seaswara will know why we want small data on by default, because I don't. I suspect it gives better code size performance on benchmarks and that's why?
> 
> > it depends on linker support which LLD does not have
> 
> I'll keep fixing hexagon lld bugs as we encounter them. But it's worth mentioning that the vast majority of hexagon codegen put to use in real devices gets linked with `ld.eld`.
> 
> I will concede that I like the uniformity when the llvm project comes with its own linker. Though, at the same time, there's some [risk of a monoculture there too](https://lists.llvm.org/pipermail/llvm-dev/2019-June/133308.html).

@aankit-ca can you weigh in on this PR?

https://github.com/llvm/llvm-project/pull/187344