[llvm] [AArch64] Consider [u/s]itofp SVE packing costs (PR #225352)

[Sander de Smalen via llvm-commits]

================

----------------
sdesmalen-arm wrote:

What does this table have to with fixed length vectors; it only considers scalable vectors. If this is about the cost of conversions between types, I'm puzzled as to why the opcode is relevant?

https://github.com/llvm/llvm-project/pull/225352