cifs: use a flexarray in cifs_writedata

The cifs_writedata code uses a single element trailing array, which
just adds unneeded complexity. Use a flexarray instead.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -1068,7 +1068,7 @@ struct cifs_writedata {
 	unsigned int			pagesz;
 	unsigned int			tailsz;
 	unsigned int			nr_pages;
-	struct page			*pages[1];
+	struct page			*pages[];
 };
 
 /*