bonding,llc: Fix structure sizeof incompatibility for some PDUs

With some combinations of arch/compiler (e.g. arm-linux-gcc) the sizeof
operator on structure returns value greater than expected. In cases when the
structure is used for mapping PDU fields it may lead to unexpected results
(such as holes and alignment problems in skb data). __packed prevents this
undesired behavior.

Signed-off-by: Vitalii Demianets <vitas@nppfactor.kiev.ua>
Signed-off-by: David S. Miller <davem@davemloft.net>