Fix typo in scsi_transport_iscsi.c kernel-doc notation:

Warning(drivers/scsi/scsi_transport_iscsi.c:548): No description found for parameter 'cmd'
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Acked-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>