zephyr: prefix generated header path with `zephyr/`

Update the include path of generated headers.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
diff --git a/boot/zephyr/kernel/banner.c b/boot/zephyr/kernel/banner.c
index ee7b88d..f917582 100644
--- a/boot/zephyr/kernel/banner.c
+++ b/boot/zephyr/kernel/banner.c
@@ -8,8 +8,8 @@
 #include <zephyr/kernel.h>
 #include <zephyr/init.h>
 #include <zephyr/device.h>
-#include <version.h>
-#include <app_version.h>
+#include <zephyr/version.h>
+#include <zephyr/app_version.h>
 
 #if defined(CONFIG_BOOT_DELAY) && (CONFIG_BOOT_DELAY > 0)
 #define DELAY_STR STRINGIFY(CONFIG_BOOT_DELAY)