net: sched: flower: only return error from hw offload if skip_sw

Recently introduced tc_setup_flow_action() can fail when parsing tcf_exts
on some unsupported action commands. However, this should not affect the
case when user did not explicitly request hw offload by setting skip_sw
flag. Modify tc_setup_flow_action() callers to only propagate the error if
skip_sw flag is set for filter that is being offloaded, and set extack
error message in that case.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Fixes: 3a7b6861

 ("cls_api: add translator to flow_action representation")
Signed-off-by: David S. Miller <davem@davemloft.net>