blk: Drop IF_TYPE_DOC

This doesn't seem to be used for anything and it isn't clear what it is.
It dates from the first U-Boot commit.

Drop it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/disk/part.c b/disk/part.c
index 9594bb4..5f64da5 100644
--- a/disk/part.c
+++ b/disk/part.c
@@ -150,9 +150,6 @@
 	case IF_TYPE_VIRTIO:
 		printf("%s VirtIO Block Device\n", dev_desc->vendor);
 		break;
-	case IF_TYPE_DOC:
-		puts("device type DOC\n");
-		return;
 	case IF_TYPE_UNKNOWN:
 		puts("device type unknown\n");
 		return;
@@ -266,9 +263,6 @@
 	case IF_TYPE_USB:
 		puts ("USB");
 		break;
-	case IF_TYPE_DOC:
-		puts ("DOC");
-		break;
 	case IF_TYPE_MMC:
 		puts ("MMC");
 		break;
@@ -782,9 +776,6 @@
 	case IF_TYPE_USB:
 		devtype = "usbd";
 		break;
-	case IF_TYPE_DOC:
-		devtype = "docd";
-		break;
 	case IF_TYPE_MMC:
 	case IF_TYPE_SD:
 		devtype = "mmcsd";
diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
index 1a6e8f8..f16cb27 100644
--- a/drivers/block/blk-uclass.c
+++ b/drivers/block/blk-uclass.c
@@ -22,7 +22,6 @@
 	[IF_TYPE_SCSI]		= "scsi",
 	[IF_TYPE_ATAPI]		= "atapi",
 	[IF_TYPE_USB]		= "usb",
-	[IF_TYPE_DOC]		= "doc",
 	[IF_TYPE_MMC]		= "mmc",
 	[IF_TYPE_SD]		= "sd",
 	[IF_TYPE_SATA]		= "sata",
@@ -39,7 +38,6 @@
 	[IF_TYPE_SCSI]		= UCLASS_SCSI,
 	[IF_TYPE_ATAPI]		= UCLASS_INVALID,
 	[IF_TYPE_USB]		= UCLASS_MASS_STORAGE,
-	[IF_TYPE_DOC]		= UCLASS_INVALID,
 	[IF_TYPE_MMC]		= UCLASS_MMC,
 	[IF_TYPE_SD]		= UCLASS_INVALID,
 	[IF_TYPE_SATA]		= UCLASS_AHCI,
diff --git a/include/blk.h b/include/blk.h
index 5bdffe7..1898ebd 100644
--- a/include/blk.h
+++ b/include/blk.h
@@ -33,7 +33,6 @@
 	IF_TYPE_SCSI,
 	IF_TYPE_ATAPI,
 	IF_TYPE_USB,
-	IF_TYPE_DOC,
 	IF_TYPE_MMC,
 	IF_TYPE_SD,
 	IF_TYPE_SATA,