Radeon Displayable DCC Gets Enabled For Navi 12 + Navi 14 GPUs

Adding to the last minute AMD Radeon additions for making the Mesa 20.1 feature cut-off is enabling displayable DCC support for Navi 12 and Navi 14 graphics processors.

GFX10/Navi has already supported delta color compression for saving video memory bandwidth while this change is about "displayable DCC", or DCC for surfaces being scanned out to the display for benefiting from color compression.

AMD added displayable DCC back with Raven Ridge Up to now the AMD Mesa code has just enabled display DCC for Raven/Raven 2 APUs along with Renoir. But now paired with the latest Linux kernel and Mesa Git, display DCC should be working for Navi 12 and Navi 14 GPUs for further bandwidth savings with this lossless compression means. There isn't any support in place for display DCC on Navi 10.

This displayable DCC for Navi 12/14 was merged this morning via this MR ahead of the upcoming Mesa 20.1 feature freeze.