arch: 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/arch/arm/include/asm/arch-mxs/sys_proto.h b/arch/arm/include/asm/arch-mxs/sys_proto.h
index 17afd1b..f8a5649 100644
--- a/arch/arm/include/asm/arch-mxs/sys_proto.h
+++ b/arch/arm/include/asm/arch-mxs/sys_proto.h
@@ -14,7 +14,7 @@
 int mxsmmc_initialize(struct bd_info *bis, int id, int (*wp)(int),
 		      int (*cd)(int));
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 
 #if defined(CONFIG_MX23)
 #include <asm/arch/iomux-mx23.h>