Ensure that that both the start and last addresses are within
the same guest page.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230629082522.606219-3-mark.cave-ayland@ilande.co.uk>
[rth: Use tcg_debug_assert, simplify the expression]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>