hw/sd/sdcard: Do not abort when reading DAT lines on invalid cmd state

hw/sd/sdcard: Do not abort when reading DAT lines on invalid cmd state

Guest should not try to read the DAT lines from invalid
command state. If it still insists to do so, return a
dummy value.

Cc: qemu-stable@nongnu.org
Fixes: e2dec2eab0 ("hw/sd/sdcard: Remove default case in read/write on DAT lines")
Reported-by: Zheyu Ma <zheyuma97@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2454
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20240730092138.32443-3-philmd@linaro.org>