[parseopt] Refer to online documentation for command help

The online documentation (e.g. http://ipxe.org/cmd/ifopen), though not
yet complete, is far more comprehensive than could be provided within
the iPXE binary.  Save around 200 bytes (compressed) by removing the
command descriptions from the interactive help, and instead referring
users directly to the web page describing the relevant command.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/parseopt.h

@@ -81,12 +81,12 @@ struct command_descriptor {
 	uint8_t min_args;
 	/** Maximum number of non-option arguments */
 	uint8_t max_args;
-	/** Command usage and description
+	/** Command usage
 	 *
 	 * This excludes the literal "Usage:" and the command name,
 	 * which will be prepended automatically.
 	 */
-	const char *usage_description;
+	const char *usage;
 };
 
 /** No maximum number of arguments */
@@ -99,11 +99,9 @@ struct command_descriptor {
  * @v _options		Option descriptor array
  * @v _check_args	Remaining argument checker
  * @v _usage		Command usage
- * @v _description	Command description
  * @ret _command	Command descriptor
  */
-#define COMMAND_DESC( _struct, _options, _min_args, _max_args, _usage,	      \
-		      _description )					      \
+#define COMMAND_DESC( _struct, _options, _min_args, _max_args, _usage )	      \
 	{								      \
 		.options = ( ( ( ( typeof ( _options[0] ) * ) NULL ) ==	      \
 			       ( ( struct option_descriptor * ) NULL ) ) ?    \
@@ -113,7 +111,7 @@ struct command_descriptor {
 		.len = sizeof ( _struct ),				      \
 		.min_args = _min_args,					      \
 		.max_args = _max_args,					      \
-		.usage_description = _usage "\n\n" _description,	      \
+		.usage = _usage,					      \
 	 }
 
 extern int parse_string ( const char *text, const char **value );