bonding: add arp_ip_target checks when install the module

When I install the bonding with the wrong arp_ip_target,
just like arp_ip_target=500.500.500.500, the arp_ip_target
was transfored to 245.245.245.244 and stored in the ip
target success, it is uncorrect, so I add checks to avoid
adding wrong address.

The in4_pton() will set wrong ip address to 0.0.0.0 and
return 0, also use the micro IS_IP_TARGET_UNUSABLE_ADDRESS
to simplify the code.

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>