anv: finish the binding_table_pool on destroyDevice when use_softpin

anv: finish the binding_table_pool on destroyDevice when use_softpin

Running VK-CTS in batch execution mode was raising the
VK_ERROR_INITIALIZATION_FAILED error in multiple tests. But when the
same failing tests were run isolated they always passed.

createDevice and destroyDevice were called before and after every
tests. Because the binding_table_pool was never closed, we reached the
maximum number of open file descriptors (ulimit -n) and when that
happened every call to createDevice implied a
VK_ERROR_INITIALIZATION_FAILED error.

Fixes: c7db0ed4e94dce563d722e1b098684fbd7315d51
      ("anv: Use a separate pool for binding tables when soft pinning")

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>