anv: Initialize the clear color more often for FCV

What does this MR do and why?

Instead of only initializing the clear color when the first subresource is accessed, initialize it for every FCV-enabled subresource. This is needed because writes to any subresource may be converted to fast clears.

Now that init_fast_clear_color is called for every subresource, we take care not to stomp on the fast-clear-tracking state of the first subresource by moving the code which updates it outside of init_fast_clear_color.

Now init_fast_clear_color does just what it says: initializes the fast clear color.

This fixes the regression introduced with commit 57445adc, ("anv: Re-enable CCS_E on TGL+").

Cc: mesa-stable

Closes: #8461 (closed)