[SCSI] iscsi: pass target nr to session creation

So the drivers do not use the channel numbers, but some do
use the target numbers. We were just adding some goofy
variable that just increases for the target nr. This is useless
for software iscsi because it is always zero. And for qla4xxx
the target nr is actually the index of the target/session
in its FW or FLASH tables. We needed to expose this to userspace
so apps could access those numbers so this patch just adds the
target nr to the iscsi session creation functions. This way
when qla4xxx's Hw thinks a session is at target nr 4
in its hw, it is exposed as that number in sysfs.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>