[llvm] GlobalISel: Use G_UADDE when narrowing G_UMULH (PR #97194)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Why is AArch64 not affected? Missing test coverage?
> 
> My guess is since it has a 64-bit multiply, this will typically be unused. The test coverage for really wide multiplies is probably lacking

Yes, missing tests. It has 64-bit umulh, so I have to go all the way to an i160 multiply before I see this expansion kick in 

https://github.com/llvm/llvm-project/pull/97194