ESP32-S2: fix - use correct storage label

This is a bugfix. It uses the right storage label `slot0_partition` for
esp32s2. Note that this is already the case for esp32 and esp32s3.

This should address
https://github.com/zephyrproject-rtos/zephyr/issues/55286

.

Signed-off-by: Ning Shang <syncom.dev@gmail.com>