[llvm] [AMDGPU] Prevent SDWA 'preserve' transformation for instructions in different basic blocks. (PR #82406)

[Valery Pykhtin via llvm-commits]

vpykhtin wrote:

> Why not allow the optimization, and just fix the "Move MI before v_or_b32" code in `convertToSDWA`?

I'm not sure it's safe to move instructions across possible execmask change.

https://github.com/llvm/llvm-project/pull/82406