doc: driver-model: there is no UCLASS_ETHERNET

%s/UCLASS_ETHERNET/UCLASS_ETH/g

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/driver-model/design.rst b/doc/driver-model/design.rst
index 5247ecc..e37b51b 100644
--- a/doc/driver-model/design.rst
+++ b/doc/driver-model/design.rst
@@ -579,7 +579,7 @@
 up) uclass::
 
    xhci_usb (UCLASS_USB)
-      eth (UCLASS_ETHERNET)
+      eth (UCLASS_ETH)
       camera (UCLASS_CAMERA)
       flash (UCLASS_FLASH_STORAGE)