Makefile: Add a u-boot.cfg file for VPL

Create this file for VPL as well, for consistency.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/Makefile b/Makefile
index 525576f..300cee2 100644
--- a/Makefile
+++ b/Makefile
@@ -624,7 +624,7 @@
 	@# Otherwise, 'make silentoldconfig' would be invoked twice.
 	$(Q)touch include/config/auto.conf
 
-u-boot.cfg spl/u-boot.cfg tpl/u-boot.cfg:
+u-boot.cfg spl/u-boot.cfg tpl/u-boot.cfg vpl/u-boot.cfg:
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf $(@)
 
 -include include/autoconf.mk