include: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Use the new symbol to refer to any 'SPL' build, including TPL and VPL

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/pico-imx8mq.h b/include/configs/pico-imx8mq.h
index 422b89a..3012f64 100644
--- a/include/configs/pico-imx8mq.h
+++ b/include/configs/pico-imx8mq.h
@@ -9,7 +9,7 @@
 #include <linux/sizes.h>
 #include <asm/arch/imx-regs.h>
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 /*#define CONFIG_ENABLE_DDR_TRAINING_DEBUG*/
 
 /* malloc f used before GD_FLG_FULL_MALLOC_INIT set */