[mubi] Fix path in auto-gen header

Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
diff --git a/hw/ip/prim/prim_mubi.core b/hw/ip/prim/prim_mubi.core
index 115e681..55014d7 100644
--- a/hw/ip/prim/prim_mubi.core
+++ b/hw/ip/prim/prim_mubi.core
@@ -6,7 +6,7 @@
 # ------------------- W A R N I N G: A U T O - G E N E R A T E D   C O D E !! -------------------//
 # PLEASE DO NOT HAND-EDIT THIS FILE. IT HAS BEEN AUTO-GENERATED WITH THE FOLLOWING COMMAND:
 #
-#    hw/ip/prim/util/generate_prim_mubi.py
+#    util/design/gen-mubi.py
 #
 name: "lowrisc:prim:mubi:0.1"
 description: "Multibit types and functions"