fsnotify: move declaration of fsnotify_mark_connector_cachep to fsnotify.h

Move fsnotify_mark_connector_cachep to fsnotify.h to properly
share it with the user in mark.c and avoid the following warning
from sparse:

fs/notify/mark.c:82:19: warning: symbol 'fsnotify_mark_connector_cachep' was not declared. Should it be static?

Link: https://lore.kernel.org/r/20191015132518.21819-1-ben.dooks@codethink.co.ukSigned-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/fsnotify.c

@@ -381,8 +381,6 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
 }
 EXPORT_SYMBOL_GPL(fsnotify);
 
-extern struct kmem_cache *fsnotify_mark_connector_cachep;
-
 static __init int fsnotify_init(void)
 {
 	int ret;

fs/notify/fsnotify.h

@@ -65,4 +65,6 @@ extern void __fsnotify_update_child_dentry_flags(struct inode *inode);
 extern struct fsnotify_event_holder *fsnotify_alloc_event_holder(void);
 extern void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder);
 
+extern struct kmem_cache *fsnotify_mark_connector_cachep;
+
 #endif	/* __FS_NOTIFY_FSNOTIFY_H_ */