ata: Only output sg element mapped number in verbose debug

Defining `ATA_DEBUG` there are a lof of messages like below in the log.

    [   16.345472] ata_sg_setup: 1 sg elements mapped

As that is too verbose, only output these messages in verbose debug.
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libata-core.c

@@ -5063,7 +5063,7 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
 	if (n_elem < 1)
 		return -1;
 
-	DPRINTK("%d sg elements mapped\n", n_elem);
+	VPRINTK("%d sg elements mapped\n", n_elem);
 	qc->orig_n_elem = qc->n_elem;
 	qc->n_elem = n_elem;
 	qc->flags |= ATA_QCFLAG_DMAMAP;