radv: fix updating bound fast ds clear values with different aspects

On GFX9, the driver is able to do an optimized fast depth/stencil
clear with only one aspect (ie. clear the stencil part of a
depth/stencil image). When this happens, the driver should only
update the clear values of the given aspect.

Note that it's currently only supported on GFX9 but I have some
local patches that extend this optimized path for other gens.

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1967


Cc: 19.2 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit a1332037)