global: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Complete this rename for all directories outside arch/ board/ drivers/
and include/

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/common/spl/Makefile b/common/spl/Makefile
index 137b184..10528b3 100644
--- a/common/spl/Makefile
+++ b/common/spl/Makefile
@@ -6,7 +6,7 @@
 # Based on common/Makefile.
 #
 
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 obj-$(CONFIG_$(SPL_TPL_)FRAMEWORK) += spl.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTROM_SUPPORT) += spl_bootrom.o
 obj-$(CONFIG_$(SPL_TPL_)LOAD_FIT) += spl_fit.o