[llvm] [AArch64][GlobalISel] Don't crash when legalising G_*MIN/G_*MAX of pointer vector (PR #168872)

[Nathan Corbyn via llvm-commits]

cofibrant wrote:

Just wanted to check in and ask how best to move this forward. I'm more than happy to work on modifying the IR verifiers (both for LLVM and gMIR) to rule out this kind of operation given some guidance on the expected behaviour.

https://github.com/llvm/llvm-project/pull/168872