GFX12 swizzle mode and GCC formats changed and is much simpler. Use a
seperate function for the same. Changes:

* Swizzle mode is now 3 bits only
* DCC enablement doesn't come from tiling_flags, it is always set in modifiers
* DCC max compressed block size of 128B
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>