iSCSI: strengthening queue condition on pg 37 [v 15]

[Luben Tuikov <luben@splentec.com>]

The condition on page 37:

-If the PDU MaxCmdSN is less than the PDU ExpCmdSN-1 (in Serial
Arithmetic Sense), they are both ignored.

can be strengthened by specifying ``less than or equal''.
Then and only then is the queue size > 0.

-- 
Luben

P.S. Proof: Ignore* if  maxcmdsn <= expcmdsn-1.
Thus accept if maxcmdsn > expcmdsn-1,
which is maxcmdsn-expcmdsn+1 > 0,
but maxcmdsn-expcmdsn+1 is the queue size,
so accept* only if queue size > 0.

*Meaning ignore/accept the values of maxcmdsn and expcmdsn.