boot: zephyr: Fix included header

Rename the header file after upstream change.

Signed-off-by: Marek Matej <marek.matej@espressif.com>
diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index 7429969..0e6e0f8 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -49,7 +49,7 @@
 #ifdef CONFIG_SOC_FAMILY_ESPRESSIF_ESP32
 
 #include <bootloader_init.h>
-#include <esp_loader.h>
+#include <esp_image_loader.h>
 
 #define IMAGE_INDEX_0   0
 #define IMAGE_INDEX_1   1