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/include/dm/uclass-id.h b/include/dm/uclass-id.h
index cbf9b2c..a5cf6e2 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -26,11 +26,11 @@
 
 	/* U-Boot uclasses start here - in alphabetical order */
 	UCLASS_ADC,		/* Analog-to-digital converter */
+	UCLASS_AHCI,		/* SATA disk controller */
 	UCLASS_BLK,		/* Block device */
 	UCLASS_CLK,		/* Clock source, e.g. used by peripherals */
 	UCLASS_CPU,		/* CPU, typically part of an SoC */
 	UCLASS_CROS_EC,		/* Chrome OS EC */
-	UCLASS_DISK,		/* Disk controller, e.g. SATA */
 	UCLASS_DISPLAY,		/* Display (e.g. DisplayPort, HDMI) */
 	UCLASS_DMA,		/* Direct Memory Access */
 	UCLASS_RAM,		/* RAM controller */