proc: make the proc_create[_data]() stubs static inlines

Change the proc_create[_data]() stubs which are used when CONFIG_PROC_FS
is not set from #defines to a static inline stubs.

This should fix clang -Werror builds failing due to errors like this:

  drivers/platform/x86/thinkpad_acpi.c:918:30: error: unused variable
   'dispatch_proc_ops' [-Werror,-Wunused-const-variable]

Fixing this in include/linux/proc_fs.h should ensure that the same issue
is also fixed in any other drivers hitting the same -Werror issue.

[akpm@linux-foundation.org: fix CONFIG_PROC_FS=n]
[akpm@linux-foundation.org: fix arch/sparc/kernel/led.c]
[akpm@linux-foundation.org: fix build]

Link: https://lkml.kernel.org/r/20211116131112.508304-1-hdegoede@redhat.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/sparc/kernel/led.c

@@ -114,18 +114,16 @@ static const struct proc_ops led_proc_ops = {
 };
 #endif
 
-static struct proc_dir_entry *led;
-
 #define LED_VERSION	"0.1"
 
 static int __init led_init(void)
 {
 	timer_setup(&led_blink_timer, led_blink, 0);
 
-	led = proc_create("led", 0, NULL, &led_proc_ops);
-	if (!led)
+#ifdef CONFIG_PROC_FS
+	if (!proc_create("led", 0, NULL, &led_proc_ops))
 		return -ENOMEM;
-
+#endif
 	printk(KERN_INFO
 	       "led: version %s, Lars Kotthoff <metalhead@metalhead.ws>\n",
 	       LED_VERSION);

include/linux/proc_fs.h

@@ -178,8 +178,16 @@ static inline struct proc_dir_entry *proc_mkdir_mode(const char *name,
 #define proc_create_seq(name, mode, parent, ops) ({NULL;})
 #define proc_create_single(name, mode, parent, show) ({NULL;})
 #define proc_create_single_data(name, mode, parent, show, data) ({NULL;})
-#define proc_create(name, mode, parent, proc_ops) ({NULL;})
-#define proc_create_data(name, mode, parent, proc_ops, data) ({NULL;})
+
+static inline struct proc_dir_entry *
+proc_create(const char *name, umode_t mode, struct proc_dir_entry *parent,
+	    const struct proc_ops *proc_ops)
+{ return NULL; }
+
+static inline struct proc_dir_entry *
+proc_create_data(const char *name, umode_t mode, struct proc_dir_entry *parent,
+		 const struct proc_ops *proc_ops, void *data)
+{ return NULL; }
 
 static inline void proc_set_size(struct proc_dir_entry *de, loff_t size) {}
 static inline void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid) {}