mm/migrate.c: attach_page_private already does the get_page

Just finished bisecting mmotm, to find why a test which used to take
four minutes now took more than an hour: the __buffer_migrate_page()
cleanup left behind a get_page() which attach_page_private() now does.

Fixes: cd0f3715 ("mm/migrate.c: call detach_page_private to cleanup code")
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/migrate.c

@@ -798,7 +798,6 @@ static int __buffer_migrate_page(struct address_space *mapping,
 		goto unlock_buffers;
 
 	attach_page_private(newpage, detach_page_private(page));
-	get_page(newpage);
 
 	bh = head;
 	do {