blk: Switch over to using uclass IDs

We currently have an if_type (interface type) and a uclass id. These are
closely related and we don't need to have both.

Drop the if_type values and use the uclass ones instead.

Maintain the existing, subtle, one-way conversion between UCLASS_USB and
UCLASS_MASS_STORAGE for now, and add a comment.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/efi_driver/efi_block_device.c b/lib/efi_driver/efi_block_device.c
index d57d281..3177ab6 100644
--- a/lib/efi_driver/efi_block_device.c
+++ b/lib/efi_driver/efi_block_device.c
@@ -128,7 +128,7 @@
 	if (!obj)
 		return -ENOENT;
 
-	devnum = blk_find_max_devnum(IF_TYPE_EFI_LOADER);
+	devnum = blk_find_max_devnum(UCLASS_EFI_LOADER);
 	if (devnum == -ENODEV)
 		devnum = 0;
 	else if (devnum < 0)
@@ -140,7 +140,7 @@
 	sprintf(name, "efiblk#%d", devnum);
 
 	/* Create driver model udevice for the EFI block io device */
-	ret = blk_create_device(parent, "efi_blk", name, IF_TYPE_EFI_LOADER,
+	ret = blk_create_device(parent, "efi_blk", name, UCLASS_EFI_LOADER,
 				devnum, io->media->block_size,
 				(lbaint_t)io->media->last_block, &bdev);
 	if (ret)