[llvm] [AMDGPU][GlobalISel] Update G_TRUNC tests (PR #180647)

[Petar Avramovic via llvm-commits]

https://github.com/petar-avramovic requested changes to this pull request.

Need to be much more careful with patches like this.
For some tests it was missed to switch to new-reg-bank-select, but it is not just because of G_TRUNC but many other opcodes (fix title)
but great amount here was not meant to be switched or reason for having -global-isel-abort=2 was not yet fixed

https://github.com/llvm/llvm-project/pull/180647