board: 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/board/toradex/apalis_imx6/pf0100.c b/board/toradex/apalis_imx6/pf0100.c
index 157aaec..7ea9bbb 100644
--- a/board/toradex/apalis_imx6/pf0100.c
+++ b/board/toradex/apalis_imx6/pf0100.c
@@ -212,7 +212,7 @@
 	return programmed;
 }
 
-#ifndef CONFIG_SPL_BUILD
+#ifndef CONFIG_XPL_BUILD
 static int pf0100_prog(void)
 {
 	int rc;
@@ -280,4 +280,4 @@
 	"Program the OTP fuses on the PMIC PF0100",
 	""
 );
-#endif /* CONFIG_SPL_BUILD */
+#endif /* CONFIG_XPL_BUILD */