ibft: fix target info parsing in ibft module

I got this patch through Red Hat's bugzilla from the bug submitter and
patch creator.  I have just fixed it up so it applies without fuzz to
upstream kernels.

Original patch and description from Shyam kumar Iyer:

The issue [ibft module not displaying targets with short names] is because
of an offset calculatation error in the iscsi_ibft.c code.  Due to this
error directory structure for the target in /sys/firmware/ibft does not
get created and so the initiator is unable to connect to the target.

Note that this bug surfaced only with an name that had a short section at
the end.  eg: "iqn.1984-05.com.dell:dell".  It did not surface when the
iqn's had a longer section at the end.  eg:
"iqn.2001-04.com.example:storage.disk2.sys1.xyz"

So, the eot_offset was calculated such that an extra 48 bytes i.e.  the
size of the ibft_header which has already been accounted was subtracted
twice.

This was not evident with longer iqn names because they would overshoot
the total ibft length more than 48 bytes and thus would escape the bug.

Signed-off-by: Shyam Kumar Iyer <shyam_iyer@dell.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Cc: Konrad Rzeszutek <konrad@virtualiron.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/firmware/iscsi_ibft.c

@@ -669,8 +669,7 @@ static int __init ibft_register_kobjects(struct ibft_table_header *header,
 
 	control = (void *)header + sizeof(*header);
 	end = (void *)control + control->hdr.length;
-	eot_offset = (void *)header + header->length -
-		     (void *)control - sizeof(*header);
+	eot_offset = (void *)header + header->length - (void *)control;
 	rc = ibft_verify_hdr("control", (struct ibft_hdr *)control, id_control,
 			     sizeof(*control));