[llvm] [AMDGPU][GFX12] Restrict scalar subword loads to PAL (PR #117576)

[Juan Manuel Martinez Caamaño via llvm-commits]

jmmartinez wrote:

In that case I propose by default not emitting the subscalar s_buffer_loads for gfx12 (for all platforms), unless some `-gfx12-force-subscalar-s-buffer-loads` option is passed to the backend (as a workaround for SWDEV-498239, and useful for us for testing).

What do you think?

https://github.com/llvm/llvm-project/pull/117576