include: 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/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index d6c15e2..644a0d7 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -55,7 +55,7 @@
 	 * @cur_serial_dev: current serial device
 	 */
 	struct udevice *cur_serial_dev;
-#ifndef CONFIG_SPL_BUILD
+#ifndef CONFIG_XPL_BUILD
 	/**
 	 * @jt: jump table
 	 *