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-socfpga/Makefile b/arch/arm/mach-socfpga/Makefile
index 67c6a8d..5fc61b4 100644
--- a/arch/arm/mach-socfpga/Makefile
+++ b/arch/arm/mach-socfpga/Makefile
@@ -80,7 +80,7 @@
 obj-y	+= wrap_pll_config_soc64.o
 endif
 
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 ifdef CONFIG_TARGET_SOCFPGA_GEN5
 obj-y	+= spl_gen5.o
 obj-y	+= freeze_controller.o