iavf: use tc_cls_can_offload_and_chain0() instead of chain check

Looks like the iavf code actually experienced a race condition, when a
developer took code before the check for chain 0 was put to helper.
So use tc_cls_can_offload_and_chain0() helper instead of direct check and
move the check to _cb() so this is similar to i40e code.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>