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/x86/lib/fsp/Makefile b/arch/x86/lib/fsp/Makefile
index da6c0a8..0039dd1 100644
--- a/arch/x86/lib/fsp/Makefile
+++ b/arch/x86/lib/fsp/Makefile
@@ -4,7 +4,7 @@
 
 obj-y += fsp_common.o
 obj-y += fsp_dram.o
-ifndef CONFIG_SPL_BUILD
+ifndef CONFIG_XPL_BUILD
 obj-$(CONFIG_VIDEO_FSP) += fsp_graphics.o
 endif
 obj-y += fsp_support.o