open-plc-utils: Force creation of open-plc-utils metapackage

Without it, all other plugin packages are not installable.

Fixes #3481

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

utils/open-plc-utils/Makefile

@@ -91,6 +91,7 @@ define Build/Compile
 endef
 
 define Package/open-plc-utils/install
+	true
 endef
 
 define BuildPlugin