dm: Rename disk uclass to ahci

This started as 'ahci' and was renamed to 'disk' during code review. But it
seems that this is too generic. Now that we have a 'blk' uclass, we can use
that as the generic piece, and revert to ahci for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/ivybridge/sata.c b/arch/x86/cpu/ivybridge/sata.c
index c3d1057..1ce8195 100644
--- a/arch/x86/cpu/ivybridge/sata.c
+++ b/arch/x86/cpu/ivybridge/sata.c
@@ -233,7 +233,7 @@
 
 U_BOOT_DRIVER(ahci_ivybridge_drv) = {
 	.name		= "ahci_ivybridge",
-	.id		= UCLASS_DISK,
+	.id		= UCLASS_AHCI,
 	.of_match	= bd82x6x_ahci_ids,
 	.probe		= bd82x6x_sata_probe,
 };