aco/gfx8: use ds_swizzle_b32 rotate mode
Despite only being mentioned in the ISA docs since vega, rotate (and fft) swizzle mode seem to exist since gfx8.
https://github.com/llvm/llvm-project/issues/28975#issuecomment-980964939
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Despite only being mentioned in the ISA docs since vega, rotate (and fft) swizzle mode seem to exist since gfx8.
https://github.com/llvm/llvm-project/issues/28975#issuecomment-980964939