[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/ata_generic.c b/drivers/ata/ata_generic.c
index 0878fb5..430fcf4 100644
--- a/drivers/ata/ata_generic.c
+++ b/drivers/ata/ata_generic.c
@@ -146,7 +146,7 @@
 		.flags = ATA_FLAG_SLAVE_POSS,
 		.pio_mask = 0x1f,
 		.mwdma_mask = 0x07,
-		.udma_mask = 0x3f,
+		.udma_mask = ATA_UDMA5,
 		.port_ops = &generic_port_ops
 	};
 	const struct ata_port_info *ppi[] = { &info, NULL };