[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/aha1740.c

@@ -347,7 +347,7 @@ static int aha1740_queuecommand(Scsi_Cmnd * SCpnt, void (*done)(Scsi_Cmnd *))
 {
 	unchar direction;
 	unchar *cmd = (unchar *) SCpnt->cmnd;
-	unchar target = SCpnt->device->id;
+	unchar target = scmd_id(SCpnt);
 	struct aha1740_hostdata *host = HOSTDATA(SCpnt->device->host);
 	unsigned long flags;
 	void *buff = SCpnt->request_buffer;