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>
diff --git a/soc/xtensa/esp32s2/loader.c b/soc/xtensa/esp32s2/loader.c
index d401fbd..6f55149 100644
--- a/soc/xtensa/esp32s2/loader.c
+++ b/soc/xtensa/esp32s2/loader.c
@@ -30,7 +30,7 @@
 {
 	int rc = 0;
 
-	size_t _partition_offset = FIXED_PARTITION_OFFSET(image_0);
+	size_t _partition_offset = FIXED_PARTITION_OFFSET(slot0_partition);
 	uint32_t _app_irom_start = _partition_offset + (uint32_t)&_image_irom_start;
 	uint32_t _app_irom_size = (uint32_t)&_image_irom_size;
 	uint32_t _app_irom_vaddr = (uint32_t)&_image_irom_vaddr;