radv: handle layered fast clears.

radv: handle layered fast clears.

This iterates the fast clear flush across the layers in the
specified range.

It also moves the compute resolve flush into the function
and builds the range in there.

This fixes:
dEQP-VK.geometry.layered.* regressions since fast clears.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>