scripts: Define CONFIG_XPL_BUILD for all xPL builds

The new name 'xPL' is intended to indicate a build of any phase which is
not U-Boot proper. Define it for all such phases.

Note that we also define CONFIG_SPL_BUILD for all xPL builds. This
preserves existing behaviour, but future patches will adjust that.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/scripts/Makefile.autoconf b/scripts/Makefile.autoconf
index b42f9b5..d754402 100644
--- a/scripts/Makefile.autoconf
+++ b/scripts/Makefile.autoconf
@@ -83,15 +83,15 @@
 
 spl/u-boot.cfg: include/config.h FORCE
 	$(Q)mkdir -p $(dir $@)
-	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD)
+	$(call cmd,u_boot_cfg,-DCONFIG_XPL_BUILD -DCONFIG_SPL_BUILD)
 
 tpl/u-boot.cfg: include/config.h FORCE
 	$(Q)mkdir -p $(dir $@)
-	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD -DCONFIG_TPL_BUILD)
+	$(call cmd,u_boot_cfg,-DCONFIG_XPL_BUILD -DCONFIG_SPL_BUILD -DCONFIG_TPL_BUILD)
 
 vpl/u-boot.cfg: include/config.h FORCE
 	$(Q)mkdir -p $(dir $@)
-	$(call cmd,u_boot_cfg,-DCONFIG_SPL_BUILD -DCONFIG_VPL_BUILD)
+	$(call cmd,u_boot_cfg,-DCONFIG_XPL_BUILD -DCONFIG_SPL_BUILD -DCONFIG_VPL_BUILD)
 
 include/autoconf.mk: u-boot.cfg
 	$(call cmd,autoconf)