fs/netfs: declare field `proc_link` only if CONFIG_PROC_FS=y

This field is only used for the "proc" filesystem.

Signed-off-by: Max Kellermann <[e-mail]>
Signed-off-by: David Howells <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
cc: Paulo Alcantara <[e-mail]>
cc: [e-mail]
cc: [e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

include/linux/netfs.h

···
 	struct kiocb		*iocb;		/* AIO completion vector */
 	struct netfs_cache_resources cache_resources;
 	struct netfs_io_request	*copy_to_cache;	/* Request to write just-read data to the cache */
+#ifdef CONFIG_PROC_FS
 	struct list_head	proc_link;	/* Link in netfs_iorequests */
+#endif
 	struct netfs_io_stream	io_streams[2];	/* Streams of parallel I/O operations */
 #define NR_IO_STREAMS 2 //wreq->nr_io_streams
 	struct netfs_group	*group;		/* Writeback group being written back */