[SCSI] libfc, libfcoe: FDISC ELS for NPIV

Add FDISC ELS handling to libfc and libfcoe, treat it the same as FLOGI where
appropriate.

Add checking for NPIV support in the FLOGI LS_ACC service parameters.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>