iris: Enable fast clear colors on gen11.
Gen11 changes the way clear colors are specified in the surface state. The main difference is that it now has an address to a piece of memory where the clear color was stored, instead of inlining the clear color into the SURFACE_STATE.
Another change from previous generations is that the clear color also gets encoded to sRGB by the hardware during the fast clear, but this encoded version of the color is not used during resolves. So we add some extra tracking to make sure we know what to do, and encode it as needed during resolves.
This series is based on Pam's series !352 (merged) .