sandbox: mmc: Fix up MMC emulator for valgrind

At present running sandbox with valgrind produces some warnings due to the
MMC emulator not filling in all the expected fields. Fix it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: use sizeof() instead of hardcoded 16]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
1 file changed