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/imx8qxp_mek.h b/include/configs/imx8qxp_mek.h
index 9399950..1b6eb2b 100644
--- a/include/configs/imx8qxp_mek.h
+++ b/include/configs/imx8qxp_mek.h
@@ -10,7 +10,7 @@
 #include <linux/stringify.h>
 #include <asm/arch/imx-regs.h>
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 #define CFG_MALLOC_F_ADDR		0x00120000
 
 #endif