Up until now the driver returned an error when learning was enabled on a
VxLAN device enslaved to an offloaded bridge.

Previous patches added VxLAN learning support, so remove the check.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>