radv/winsys: fix executing huge secondary command buffers on GFX6
If the secondary has a list of CS buffers, it should be copied to the primary. Fixes dEQP-VK.api.command_buffers.record_many_draws_secondary_2. Cc: 21.1 mesa-stable Signed-off-by:Samuel Pitoiset <samuel.pitoiset@gmail.com> Reviewed-by:
Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl> Part-of: <mesa/mesa!10547> (cherry picked from commit 12a00da8)