Update docs/design.md

Co-authored-by: Jamie <[email protected]>

Author: de-nordic

docs/design.md

@@ -142,7 +142,7 @@ While reading unprotected TLVs from an image, MCUboot will try to match TLVs
 against list it has compiled in support for; each new defined TLV has to be added
 to that list, which is named `allowed_unprot_tlvs` and defined in
 image_validate.c. The usage of the list is optional and can be controlled
-during compilation with MCUBOOT_USE_TLV_ALLOW_LIST config identifier.
+during compilation with `MCUBOOT_USE_TLV_ALLOW_LIST` config identifier.
 
 ## [Flash map](#flash-map)