fuse: limit nsec

commit 47912eaa upstream.

Limit nanoseconds to 0..999999999.

Fixes: d8a5ba45 ("[PATCH] FUSE - core")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>