include/linux/fs.h: fix comment about struct address_space

Before commit 9c5d760b ("mm: split gfp_mask and mapping flags into
separate fields") the private_* fields of struct adrress_space were grouped
together and using "ditto" in comments describing the last fields was
correct.

With introduction of gpf_mask between private_lock and private_list "ditto"
references the wrong description.

Fix it by using the elaborate description.
Signed-off-by: NMike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

include/linux/fs.h

@@ -403,7 +403,7 @@ struct address_space {
 	unsigned long		flags;		/* error bits */
 	spinlock_t		private_lock;	/* for use by the address_space */
 	gfp_t			gfp_mask;	/* implicit gfp mask for allocations */
-	struct list_head	private_list;	/* ditto */
+	struct list_head	private_list;	/* for use by the address_space */
 	void			*private_data;	/* ditto */
 	errseq_t		wb_err;
 } __attribute__((aligned(sizeof(long)))) __randomize_layout;