dynamic_debug: add static inline stub for ddebug_add_module

For symmetry with ddebug_remove_module, and to avoid a bit of ifdeffery
in module.c, move the declaration of ddebug_add_module inside #if
defined(CONFIG_DYNAMIC_DEBUG) and add a corresponding no-op stub in the
#else branch.

Link: http://lkml.kernel.org/r/20190212214150.4807-10-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Jason Baron <jbaron@akamai.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/dynamic_debug.h

@@ -47,10 +47,10 @@ struct _ddebug {
 } __attribute__((aligned(8)));
 
 
-int ddebug_add_module(struct _ddebug *tab, unsigned int n,
-				const char *modname);
 
 #if defined(CONFIG_DYNAMIC_DEBUG)
+int ddebug_add_module(struct _ddebug *tab, unsigned int n,
+				const char *modname);
 extern int ddebug_remove_module(const char *mod_name);
 extern __printf(2, 3)
 void __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...);
@@ -152,6 +152,12 @@ do {								\
 #include <linux/string.h>
 #include <linux/errno.h>
 
+static inline int ddebug_add_module(struct _ddebug *tab, unsigned int n,
+				    const char *modname)
+{
+	return 0;
+}
+
 static inline int ddebug_remove_module(const char *mod)
 {
 	return 0;

kernel/module.c

@@ -2719,9 +2719,7 @@ static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsig
 {
 	if (!debug)
 		return;
-#ifdef CONFIG_DYNAMIC_DEBUG
 	ddebug_add_module(debug, num, mod->name);
-#endif
 }
 
 static void dynamic_debug_remove(struct module *mod, struct _ddebug *debug)