The previous code was confused, avoiding the flush of the old entry
if the new entry is invalid. We need to flush the old page if the
old entry is valid and the new page if the new entry is valid.
This bug was masked by over-flushing elsewhere.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>