[SCSI] use scmd_id(), scmd_channel() throughout code

Wrap a highly common idiom.  Makes the code easier to read, helps pave
the way for sdev->{id,channel} removal, and adds a token that can easily
by grepped-for in the future.

There are a couple sdev_id() and scmd_printk() updates thrown in as well.

Rejections fixed up and
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/psi240i.c

@@ -659,7 +659,7 @@ static int Psi240i_BiosParam (struct scsi_device *sdev, struct block_device *dev
 	{
 	POUR_DEVICE	pdev;
 
-	pdev = &(HOSTDATA(sdev->host)->device[sdev->id]);
+	pdev = &(HOSTDATA(sdev->host)->device[sdev_id(sdev)]);
 
 	geom[0] = pdev->heads;
 	geom[1] = pdev->sectors;