[llvm] [TableGen] Assign LaneBitmask bits in a less surprising order (PR #225809)

[Igor Wodiany via llvm-commits]

https://github.com/IgWod commented:

The new ordering makes more sense to me, so definitely in favor. The generic and AMDGPU changes LGTM

https://github.com/llvm/llvm-project/pull/225809