[PATCH] Honour AOP_TRUNCATE_PAGE returns in page_symlink

As prepare_write, commit_write and readpage are allowed to return
AOP_TRUNCATE_PAGE, page_symlink should respond to them.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>