mkbootimg: allow creating both boot and vendor_boot images

Change-Id: I3d061925630b7fb7b1208168b7088dd2ea17fe88
diff --git a/mkbootimg.py b/mkbootimg.py
index af9256b..d0c1e25 100644
--- a/mkbootimg.py
+++ b/mkbootimg.py
@@ -297,7 +297,6 @@
             raise ValueError('--vendor_ramdisk missing or invalid')
         write_vendor_boot_header(args)
         write_vendor_boot_data(args)
-        return
     if args.output is not None:
         if args.kernel is None:
             raise ValueError('kernel must be supplied when creating a boot image')