bonding: Fixed up a error "do not initialise statics to 0 or NULL" in bond_main.c

The error is found by the checkpatch.pl tools.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>