zephyr: fix booting address incorrect in ram-load mode

Signed-off-by: Jim Tan <KuoChun.Tan@ite.com.tw>
diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index 09a6f40..5e20cb1 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -297,8 +297,12 @@
  */
 static void do_boot(struct boot_rsp *rsp)
 {
-    uintptr_t flash_base;
     void *start;
+    
+#if defined(MCUBOOT_RAM_LOAD)
+    start = (void *)(rsp->br_hdr->ih_load_addr + rsp->br_hdr->ih_hdr_size);
+#else
+    uintptr_t flash_base;
     int rc;
 
     rc = flash_device_base(rsp->br_flash_dev_id, &flash_base);
@@ -306,6 +310,7 @@
 
     start = (void *)(flash_base + rsp->br_image_off +
                      rsp->br_hdr->ih_hdr_size);
+#endif
 
     /* Lock interrupts and dive into the entry point */
     irq_lock();