radeonsi: use a clever alignment for descriptor uploads
radeonsi: use a clever alignment for descriptor uploads

Non-VBO descriptors won't be smaller than the cache line, so simply use
the cache line size.

Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler