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-stm32mp/stm32mp1/Makefile b/arch/arm/mach-stm32mp/stm32mp1/Makefile
index ebae50f..5ae1a53 100644
--- a/arch/arm/mach-stm32mp/stm32mp1/Makefile
+++ b/arch/arm/mach-stm32mp/stm32mp1/Makefile
@@ -8,7 +8,7 @@
 obj-$(CONFIG_STM32MP13X) += stm32mp13x.o
 obj-$(CONFIG_STM32MP15X) += stm32mp15x.o
 
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 obj-y += spl.o
 obj-y += tzc400.o
 else