boot_serial: Fix include paths for zephyr builds

Fixes include paths for zephyr builds to use the system zcbor_*
files rather than the local files.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
diff --git a/boot/boot_serial/src/boot_serial.c b/boot/boot_serial/src/boot_serial.c
index a05c816..e8afbfe 100644
--- a/boot/boot_serial/src/boot_serial.c
+++ b/boot/boot_serial/src/boot_serial.c
@@ -26,7 +26,6 @@
 #include "sysflash/sysflash.h"
 
 #include "bootutil/bootutil_log.h"
-#include "zcbor_encode.h"
 
 #ifdef __ZEPHYR__
 #include <zephyr/sys/reboot.h>
@@ -37,13 +36,16 @@
 #include <zephyr/sys/crc.h>
 #include <zephyr/sys/base64.h>
 #include <hal/hal_flash.h>
+#include <zcbor_encode.h>
 #elif __ESPRESSIF__
+#include "zcbor_encode.h"
 #include <bootloader_utility.h>
 #include <esp_rom_sys.h>
 #include <esp_crc.h>
 #include <endian.h>
 #include <mbedtls/base64.h>
 #else
+#include "zcbor_encode.h"
 #include <bsp/bsp.h>
 #include <hal/hal_system.h>
 #include <hal/hal_flash.h>