Build: remove third argument of CERT_ADD_CMD_OPT

The third argument was given "true" by images, but it was moved
to TOOL_ADD_PAYLOAD.  No more caller of CERT_ADD_CMD_OPT uses this.
So, the third argument is always empty.  Remove it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/make_helpers/tbbr/tbbr_tools.mk b/make_helpers/tbbr/tbbr_tools.mk
index 82d83ca..afc007a 100644
--- a/make_helpers/tbbr/tbbr_tools.mk
+++ b/make_helpers/tbbr/tbbr_tools.mk
@@ -54,7 +54,7 @@
 $(if ${KEY_ALG},$(eval $(call CERT_ADD_CMD_OPT,${KEY_ALG},--key-alg)))
 $(if ${HASH_ALG},$(eval $(call CERT_ADD_CMD_OPT,${HASH_ALG},--hash-alg)))
 $(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key)))
-$(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key,,FWU_)))
+$(if ${ROT_KEY},$(eval $(call CERT_ADD_CMD_OPT,${ROT_KEY},--rot-key,FWU_)))
 $(if ${TRUSTED_WORLD_KEY},$(eval $(call CERT_ADD_CMD_OPT,${TRUSTED_WORLD_KEY},--trusted-world-key)))
 $(if ${NON_TRUSTED_WORLD_KEY},$(eval $(call CERT_ADD_CMD_OPT,${NON_TRUSTED_WORLD_KEY},--non-trusted-world-key)))