[sca] Switch ecc_serial to use edn in auto mode.

EDN in auto mode is required for long running captures.

Signed-off-by: Miguel Osorio <miguelosorio@google.com>
diff --git a/sw/device/sca/ecc_serial.c b/sw/device/sca/ecc_serial.c
index 2cf566a..01fa989 100644
--- a/sw/device/sca/ecc_serial.c
+++ b/sw/device/sca/ecc_serial.c
@@ -220,7 +220,7 @@
  * UART.
  */
 static void simple_serial_main(void) {
-  entropy_testutils_boot_mode_init();
+  entropy_testutils_auto_mode_init();
 
   sca_init(kScaTriggerSourceOtbn, kScaPeripheralEntropy | kScaPeripheralIoDiv4 |
                                       kScaPeripheralOtbn | kScaPeripheralCsrng |