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/fs/Makefile b/fs/Makefile
index 7b05c79..ec3e31c 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -4,7 +4,7 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 # Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
 
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 obj-$(CONFIG_FS_LOADER) += fs.o
 obj-$(CONFIG_SPL_FS_FAT) += fat/
 obj-$(CONFIG_SPL_FS_EXT4) += ext4/