radv: enable DCC for MSAA 2x textures on VI under an option

radv: enable DCC for MSAA 2x textures on VI under an option

This can be enabled with RADV_PERFTEST=dccmsaa.

DCC for MSAA textures is actually not as easy to implement. It
looks like there is some corner cases. I will improve support
incrementally.

Vega support, as well as Polaris improvements, will be added later.

No CTS changes on Polaris using RADV_DEBUG=zerovram and
RADV_PERFTEST=dccmsaa.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>