[mlir] Remove VectorToROCDL

[mlir] Remove VectorToROCDL

Between issues such as
https://github.com/llvm/llvm-project/issues/56323, the fact that this
lowering (unlike the code in amdgpu-to-rocdl) does not correctly set
up bounds checks (and thus will cause page faults on reads that might
need to be padded instead), and that fixing these problems would,
essentially, involve replicating amdgpu-to-rocdl, remove
--vector-to-rocdl for being broken. In addition, the lowering does not
support many aspects of transfer_{read,write}, like supervectors, and
may not work correctly in their presence.

We (the MLIR-based convolution generator at AMD) do not use this
conversion pass, nor are we aware of any other clients.

Migration strategies:
- Use VectorToLLVM
- If buffer ops are particularly needed in your application, use
amdgpu.raw_buffer_{load,store}

A VectorToAMDGPU pass may be introduced in the future.

Reviewed By: ThomasRaoux

Differential Revision: https://reviews.llvm.org/D129308