espressif:esp32s3: Add esp32s3 initial support

ESP32-S3 target and related files added to the Espressif port.

Signed-off-by: Almir Okato <almir.okato@espressif.com>
diff --git a/boot/espressif/port/esp_loader.c b/boot/espressif/port/esp_loader.c
index f2f7d87..1d3e55f 100644
--- a/boot/espressif/port/esp_loader.c
+++ b/boot/espressif/port/esp_loader.c
@@ -17,6 +17,8 @@
 #include "esp32/rom/uart.h"
 #elif CONFIG_IDF_TARGET_ESP32S2
 #include "esp32s2/rom/uart.h"
+#elif CONFIG_IDF_TARGET_ESP32S3
+#include "esp32s3/rom/uart.h"
 #elif CONFIG_IDF_TARGET_ESP32C3
 #include "esp32c3/rom/uart.h"
 #endif