libcxgbi : support ipv6 address host_param

libcxgbi was always returning an ipv4 address for ISCSI_HOST_PARAM_IPADDRESS,
return appropriate address based on address family

Signed-off-by: Anish Bhatt <anish@chelsio.com>
Signed-off-by: Karen Xie <kxie@chelsio.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Christoph Hellwig <hch@lst.de>