i2s: Update FIFO direct access reg on ESP32 according to the TRM

Closes: https://www.github.com/espressif/esp-idf/issues/8862

components/soc/esp32/include/soc/i2s_struct.h

@@ -13,8 +13,8 @@ extern "C" {
 #endif
 
 typedef volatile struct i2s_dev_s {
-    uint32_t reserved_0;
-    uint32_t reserved_4;
+    uint32_t fifo_wr;
+    uint32_t fifo_rd;
     union {
         struct {
             uint32_t tx_reset:       1;