mm: truncate functions are in truncate.c

Correct comment on truncate_inode_pages*() in linux/mm.h; and remove
declaration of page_unuse(), it didn't exist even in 2.2.26 or 2.4.0!
Signed-off-by: NHugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1411,8 +1411,7 @@ extern int do_munmap(struct mm_struct *, unsigned long, size_t);
 
 extern unsigned long do_brk(unsigned long, unsigned long);
 
-/* filemap.c */
-extern unsigned long page_unuse(struct page *);
+/* truncate.c */
 extern void truncate_inode_pages(struct address_space *, loff_t);
 extern void truncate_inode_pages_range(struct address_space *,
 				       loff_t lstart, loff_t lend);