[llvm] [AArch64][GlobalISel] Select *v1f16 for f16->s16 to_int_sat_gi (PR #154562)

[Kajetan Puchalski via llvm-commits]

mrkajetanp wrote:

Is it actually safe to assume that there will always be a `sxth` inserted before the value needs to be used? With asm like:
```
fcvtzs h0, h0
fmov w0, s0
```
Bits [31:16] of w0 will end up with whatever was in those same bits of s0 before the convert, whether it's 0 or otherwise. The convert doesn't zero them. In the cases I've seen when testing this the answer was yes, but I'm not sure whether that means it's guaranteed to be so.

https://github.com/llvm/llvm-project/pull/154562