radeonsi: Fix compute copies for subsampled formats.
We cannot do image stores (or render) to subsampled formats.
Reinterpret as R32_UINT instead.
si_set_shader_image_desc already uses the blockwidth from the view formats, so the image width adjustments are already implemented.
This is still icky with mipmapping on GFX9+ though, but since it is mostly a video format I don't think that will be much of an issue and broken mipmapping is still better than broken everything.
Fixes: e5167a92 "radeonsi: disable SDMA on gfx8 to fix corruption on RX 580" Closes: #2535 (closed)