bonding: remove redundant initialization of variable ret

The variable ret is being initialized with a value that is never read,
it is being updated later on.  The assignment is redundant and can be
removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>