[SCSI] dpt_i2o: fix transferred data length for scsi_set_resid()

dpt_i2o.c::adpt_i2o_to_scsi() reads the value at (reply+5) which
should contain the length in bytes of the transferred data. This
would be correct if reply was a u32 *. However it is a void * here,
so we need to read the value at (reply+20) instead.

The value at (reply+5) is usually 0xff0000, which is apparently
'large enough' and didn't cause any trouble until 2.6.27 where

commit 427e59f09fdba387547106de7bab980b7fff77be
Author: James Bottomley <[e-mail]>
Date: Sat Mar 8 18:24:17 2008 -0600

[SCSI] make use of the residue value

caused this to become visible through e.g. iostat -x .

Signed-off-by: Miquel van Smoorenburg <[e-mail]>
Cc: Stable Tree <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/dpt_i2o.c

···
 	hba_status = detailed_status >> 8;
 
 	// calculate resid for sg 
-	scsi_set_resid(cmd, scsi_bufflen(cmd) - readl(reply+5));
+	scsi_set_resid(cmd, scsi_bufflen(cmd) - readl(reply+20));
 
 	pHba = (adpt_hba*) cmd->device->host->hostdata[0];
 
···
 		case I2O_SCSI_DSC_SUCCESS:
 			cmd->result = (DID_OK << 16);
 			// handle underflow
-			if(readl(reply+5) < cmd->underflow ) {
+			if (readl(reply+20) < cmd->underflow) {
 				cmd->result = (DID_ERROR <<16);
 				printk(KERN_WARNING"%s: SCSI CMD underflow\n",pHba->name);
 			}