radv: do not add the image BO in radv_set_depth_clear_regs()

radv: do not add the image BO in radv_set_depth_clear_regs()

For the fast path, radv_fill_buffer() ensures that the BO is
already in the list. For the slow path, the depth surface is
part of the framebuffer which means the BO is added to the list
when the framebuffer is emitted.

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