net, proc: Provide PROC_FS=n fallback for proc_create_net_single_write()

Provide a CONFIG_PROC_FS=n fallback for proc_create_net_single_write().

Also provide a fallback for proc_create_net_data_write().

Fixes: 564def71 ("proc: Add a way to make network proc files writable")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org

include/linux/proc_fs.h

@@ -208,8 +208,10 @@ static inline void proc_remove(struct proc_dir_entry *de) {}
 static inline int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) { return 0; }
 
 #define proc_create_net_data(name, mode, parent, ops, state_size, data) ({NULL;})
+#define proc_create_net_data_write(name, mode, parent, ops, write, state_size, data) ({NULL;})
 #define proc_create_net(name, mode, parent, state_size, ops) ({NULL;})
 #define proc_create_net_single(name, mode, parent, show, data) ({NULL;})
+#define proc_create_net_single_write(name, mode, parent, show, write, data) ({NULL;})
 
 static inline struct pid *tgid_pidfd_to_pid(const struct file *file)
 {