bonding: Fix LACPDU rx_dropped commit.

I applied the wrong version of Jiri's bonding fix in commit
13a8e0c8 ("bonding: don't increase
rx_dropped after processing LACPDUs")

I applied v3, which introduces warnings I asked him to fix,
instead of v4 which properly takes care of those issues.

This inter-diffs such that the warnings are now gone.

Signed-off-by: David S. Miller <davem@davemloft.net>