[libata] Use ATA_UDMAx standard masks when filling driver's udma_mask info

The ATA_UDMAx masks are self-documenting, and far better than manually
writing in the hex mask.

Note that pata_it8213 mask differed from the comment.  Added a FIXME there.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/sata_vsc.c b/drivers/ata/sata_vsc.c
index 8133017..1b5d81f 100644
--- a/drivers/ata/sata_vsc.c
+++ b/drivers/ata/sata_vsc.c
@@ -371,7 +371,7 @@
 				  ATA_FLAG_MMIO,
 		.pio_mask	= 0x1f,
 		.mwdma_mask	= 0x07,
-		.udma_mask	= 0x7f,
+		.udma_mask	= ATA_UDMA6,
 		.port_ops	= &vsc_sata_ops,
 	};
 	const struct ata_port_info *ppi[] = { &pi, NULL };