appletalk: Fix compile regression

BugLink: https://bugs.launchpad.net/bugs/1828420

[ Upstream commit 27da0d2e ]

A bugfix just broke compilation of appletalk when CONFIG_SYSCTL
is disabled:

In file included from net/appletalk/ddp.c:65:
net/appletalk/ddp.c: In function 'atalk_init':
include/linux/atalk.h:164:34: error: expected expression before 'do'
 #define atalk_register_sysctl()  do { } while(0)
                                  ^~
net/appletalk/ddp.c:1934:7: note: in expansion of macro 'atalk_register_sysctl'
  rc = atalk_register_sysctl();

This is easier to avoid by using conventional inline functions
as stubs rather than macros. The header already has inline
functions for other purposes, so I'm changing over all the
macros for consistency.

Fixes: 6377f787 ("appletalk: Fix use-after-free in atalk_proc_exit")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

include/linux/atalk.h

@@ -153,16 +153,26 @@ extern int sysctl_aarp_resolve_time;
 extern int atalk_register_sysctl(void);
 extern void atalk_unregister_sysctl(void);
 #else
-#define atalk_register_sysctl()		do { } while(0)
-#define atalk_unregister_sysctl()	do { } while(0)
+static inline int atalk_register_sysctl(void)
+{
+	return 0;
+}
+static inline void atalk_unregister_sysctl(void)
+{
+}
 #endif
 
 #ifdef CONFIG_PROC_FS
 extern int atalk_proc_init(void);
 extern void atalk_proc_exit(void);
 #else
-#define atalk_proc_init()	({ 0; })
-#define atalk_proc_exit()	do { } while(0)
+static inline int atalk_proc_init(void)
+{
+	return 0;
+}
+static inline void atalk_proc_exit(void)
+{
+}
 #endif /* CONFIG_PROC_FS */
 
 #endif /* __LINUX_ATALK_H__ */