ipoib: returned back addrlen check for mc addresses

Apparently bogus mc address can break IPOIB multicast processing. Therefore
returning the check for addrlen back until this is resolved in bonding (I don't
see any other point from where mc address with non-dev->addr_len length can came
from).

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