dpaa2-eth: fix draining of S/G cache

On link down, the draining of the S/G cache should be done on all
_possible_ CPUs not just the ones that are online in that moment.
Fix this by changing the iterator.

Fixes: d70446ee

 ("dpaa2-eth: send a scatter-gather FD instead of realloc-ing")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>