Nobody uses the CONFIG_ATFILE test now, so just drop it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Tested-by: Claudio Fontana <claudio.fontana@huawei.com>
Message-id: 1370126121-22975-3-git-send-email-peter.maydell@linaro.org