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-tegra/tegra30/Makefile b/arch/arm/mach-tegra/tegra30/Makefile
index ee0e6f5..5edc7c9 100644
--- a/arch/arm/mach-tegra/tegra30/Makefile
+++ b/arch/arm/mach-tegra/tegra30/Makefile
@@ -2,7 +2,7 @@
 #
 # Copyright (c) 2010-2012, NVIDIA CORPORATION.  All rights reserved.
 
-obj-$(CONFIG_SPL_BUILD) += cpu.o
+obj-$(CONFIG_XPL_BUILD) += cpu.o
 obj-$(CONFIG_$(SPL_)CMD_EBTUPDATE) += bct.o
 
 obj-y	+= clock.o