radv: optimize CmdClear{Color,DepthStencil}Image() for layered textures

radv: optimize CmdClear{Color,DepthStencil}Image() for layered textures

If all layers are bound we can perform a fast color or depth clear
instead of iterating over all layers. This has the advantage
to avoid trashing the framebuffer for nothing if you we end up by
doing a fast clear when calling radv_clear_image_layer(), and
clearing all layers in one shot is obviously faster.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>