xtensa: nxp_imx8ulp_adsp: Add missing include header

Add missing header to fix imx8ulp_adsp toolchain.

Fixes: e88c208 ("xtensa: Add 8ulp_adsp toolchain")
Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>

Author: iuliana-prodan

overlays/xtensa_nxp_imx8ulp_adsp/gdb/gdb/xtensa-config.c

@@ -23,6 +23,7 @@
 
 #define XTENSA_CONFIG_VERSION 0x70
 
+#include "defs.h"
 #include "xtensa-config.h"
 #include "xtensa-tdep.h"