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-rockchip/rk3036/Makefile b/arch/arm/mach-rockchip/rk3036/Makefile
index 299fc50..038180c 100644
--- a/arch/arm/mach-rockchip/rk3036/Makefile
+++ b/arch/arm/mach-rockchip/rk3036/Makefile
@@ -6,7 +6,7 @@
 
 obj-y += clk_rk3036.o
 
-ifndef CONFIG_SPL_BUILD
+ifndef CONFIG_XPL_BUILD
 obj-y += syscon_rk3036.o
 endif