blk: Rename if_type to uclass_id

Use the word 'uclass' instead of 'if_type' to complete the conversion.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/partitions.rst b/doc/usage/partitions.rst
index 2c1a12b..628469b 100644
--- a/doc/usage/partitions.rst
+++ b/doc/usage/partitions.rst
@@ -20,7 +20,7 @@
 interface
         The interface used to access the partition's device, like ``mmc`` or
         ``scsi``. For a full list of supported interfaces, consult the
-        ``if_typename_str`` array in ``drivers/block/blk-uclass.c``
+        ``uclass_idname_str`` array in ``drivers/block/blk-uclass.c``
 
 devnum
         The device number. This defaults to 0.