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/mach-imx/imx9/lowlevel_init.S b/arch/arm/mach-imx/imx9/lowlevel_init.S
index 1dc1dbf..97d8591 100644
--- a/arch/arm/mach-imx/imx9/lowlevel_init.S
+++ b/arch/arm/mach-imx/imx9/lowlevel_init.S
@@ -16,7 +16,7 @@
 
 .global save_boot_params
 save_boot_params:
-#ifndef CONFIG_SPL_BUILD
+#ifndef CONFIG_XPL_BUILD
 	/* The firmware provided ATAG/FDT address can be found in r2/x0 */
 	adr	x0, rom_pointer
 	stp	x1, x2, [x0], #16