[SCSI] fnic: Allow multicast and unicast address registrations for fnic

To enable FIP support in fnic, we have to register with hardware to receive
FIP solication frames on a well-known multicast address.
Before FIP support, the firmware interface allowed multicast address
registrations only for enic devices. This is a minor change in fnic to
allow the firmware interface to now register mcast addresses for fnic too.

Signed-off-by: Brian Uchino <buchino@cisco.com>
Signed-off-by: Herman Lee <hermlee@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>