[llvm] [GISEL] G_SPLAT_VECTOR can take a splat that is larger than the vector element (PR #86974)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

I am again confused. You want to take i64 splats on 32-bit machines and truncate the i64 to i32? You can just state that i64 are not legal?!?

https://github.com/llvm/llvm-project/pull/86974