There were multiple bugs, like checking SWIZZLE_MODE before checking
GFX12_SWIZZLE_MODE, which has undefined behavior.

The function had no effect before (it always returned -EINVAL).
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>