ibmveth: Fix use of ibmveth in a bridge.

ibmveth: Fix use of ibmveth in a bridge.

The check for src mac address in ibmveth_is_packet_unsupported is wrong.
Commit 6f2275433a2f wanted to shut down messages for loopback packets,
but now suppresses bridged frames, which are accepted by the hypervisor
otherwise bridging won't work at all.

Fixes: 6f2275433a2f ("ibmveth: Detect unsupported packets before sending to the hypervisor")
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
Link: https://lore.kernel.org/r/20201026104221.26570-1-msuchanek@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>