[SCSI] libfcoe: Check for order and missing critical descriptors for FIP ELS requests

As per FC-BB-5 rev.2, section 7.8.7.1, strict ordering of FIP descriptors
is required for ELS requests. Also, look for missing and duplicate critical
descriptors.

Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>