[SCSI] fcoe: Fix checking san mac address

This was fixed before in 7a7f0c7f but it's introduced again recently.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>