[SCSI] iscsi update: pass correct skb to skb_trim

>From da-x@monatomic.org:

Wrong skb is passed to skb_trim in iscsi_if_get_stats.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Alex Aizman <itn780@yahoo.com>
Signed-off-by: Dmitry Yusupov <dmitry_yus@yahoo.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>