[SCSI] iscsi: add module alias

Since iscsi transport can be built as a module and uses netlink socket
to communicate. The module should have an alias to autoload when socket
of NETLINK_ISCSI type is requested.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>