Sign stable firmware 1.4.0.

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

1.4.0/sysupgrade/stable.manifest

@@ -826,3 +826,4 @@ x86-64 1.4.0 2a61b5018f9126b297e07eb5e50e85c06d3291d53d196f70390d81b0339f1df1 gl
 x86-64 1.4.0 16436362e5e62479fc8de828988193c1d66f49c114040ff2a385b91b820f7b47e4d45872d6d47b2949b057eba1b819558133bbe95500202fcdbbc618f18d04f2 gluon-ffho-1.4.0-x86-64-sysupgrade.img.gz
 ---
 0bb6cec9afd8667f6a4c379ef1fc79f615a6b869f1a888a4ebf981c1a24c050058c87f1031b3fa11ab78ceab2a957e5012bda9a9b2fd4989c11cb79aba2eb302
+d5b08f1b7d18b1ce8a4dab97d51d51983671c7f572c4053c313c18121c833e01206c8c5ede4dcf3b64e61d9764a7c054511ac2b9dceda1f5228f120d87a49f05