There are several cases where traffic that would normally be forwarded
in silicon needs to be observed in slow path. That's achieved by
trapping such traffic, and the functions trap_install() and
trap_uninstall() realize that. However, such treatment is obviously
wrong if the device in question is actually a soft device not backed by
an ASIC.

Therefore try to trap if possible, but fall back to inserting a continue
if not.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>