generator: it doesn't actually rely on descrption

The generator tool doesn't actually rely on description, this patch
removes the dependency and adjust the only real requirement, the
SOL_FLOW_NODE_PORT_ERROR_NAME ("ERROR") macro.

Signed-off-by: Leandro Dorileo <leandro.maciel.dorileo@intel.com>

src/bin/sol-fbp-generator/Kconfig

@@ -1,4 +1,3 @@
 config FBP_GENERATOR
 	bool "fbp generator"
-	depends on NODE_DESCRIPTION
 	default y

src/lib/flow/include/sol-flow.h

@@ -261,14 +261,15 @@ void sol_flow_node_named_options_fini(struct sol_flow_node_named_options *named_
 
 #include "sol-flow-buildopts.h"
 
+#define SOL_FLOW_NODE_PORT_ERROR_NAME ("ERROR")
+
 #ifdef SOL_FLOW_NODE_TYPE_DESCRIPTION_ENABLED
 /* A node type description provides more information about a node
  * type, such as textual description, name, URL, version, author as
  * well as ports and options meta information.
  */
 
 struct sol_flow_port_description {
-#define SOL_FLOW_NODE_PORT_ERROR_NAME ("ERROR")
     const char *name; /**< port's name */
     const char *description; /**< port's description */
     const char *data_type; /**< textual representation of the port's accepted packet data type(s), e. g. "int" */