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/syscounter.c b/arch/arm/mach-imx/syscounter.c
index 922f851..96fe2c7 100644
--- a/arch/arm/mach-imx/syscounter.c
+++ b/arch/arm/mach-imx/syscounter.c
@@ -59,7 +59,7 @@
 	return usec;
 }
 
-#if !CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT) || IS_ENABLED(CONFIG_SPL_BUILD)
+#if !CONFIG_IS_ENABLED(SKIP_LOWLEVEL_INIT) || IS_ENABLED(CONFIG_XPL_BUILD)
 int timer_init(void)
 {
 	struct sctr_regs *sctr = (struct sctr_regs *)SCTR_BASE_ADDR;