[ifmgmt] Optimise prototype for ifcommon_exec()

ifcommon_exec() was long-ago marked as __attribute__((regparm(2))) in
order to minimise the size of functions that call into it.  Since
then, gPXE has added -mregparm=3 as a general compilation option, and
this "optimisation" is now counter-productive.

Change (and simplify) the prototype to minimise code size given the
current compilation conditions.

src/hci/commands/ifmgmt_cmd.c

 /**
  * Execute if<xxx> command
  *
- * @v payload		Command to execute
- * @v verb		Verb describing the action of the command
  * @v argc		Argument count
  * @v argv		Argument list
+ * @v payload		Command to execute
+ * @v verb		Verb describing the action of the command
  * @ret rc		Exit code
  */
-__attribute__ (( regparm ( 2 ) )) int
-ifcommon_exec ( int ( * payload ) ( struct net_device * ),
-		const char *verb, int argc, char **argv ) {
+int ifcommon_exec ( int argc, char **argv,
+		    int ( * payload ) ( struct net_device * ),
+		    const char *verb ) {
 	int c;
 
 	/* Parse options */
 }
 
 static int ifopen_exec ( int argc, char **argv ) {
-	return ifcommon_exec ( ifopen_payload, "Open", argc, argv );
+	return ifcommon_exec ( argc, argv, ifopen_payload, "Open" );
 }
 
 /* "ifclose" command */
 }
 
 static int ifclose_exec ( int argc, char **argv ) {
-	return ifcommon_exec ( ifclose_payload, "Close", argc, argv );
+	return ifcommon_exec ( argc, argv, ifclose_payload, "Close" );
 }
 
 /* "ifstat" command */
 }
 
 static int ifstat_exec ( int argc, char **argv ) {
-	return ifcommon_exec ( ifstat_payload, "Display status of",
-			       argc, argv );
+	return ifcommon_exec ( argc, argv,
+			       ifstat_payload, "Display status of" );
 }
 
 /** Interface management commands */

src/hci/commands/ifmgmt_cmd.h

 
 struct net_device;
 
-extern int ifcommon_exec ( int ( * payload ) ( struct net_device * ),
-			   const char *verb, int argc, char **argv )
-	__attribute__ (( regparm ( 2 ) ));
+extern int ifcommon_exec (  int argc, char **argv,
+			    int ( * payload ) ( struct net_device * ),
+			    const char *verb );
 
 #endif /* _IFMGMT_CMD_H */