vendor.sh: set need_files="n" if skipping patch

This change finally ensures that no insertions will be
attempted, on the basis that readkconfig failed; this
covers the instance whereby vcfg was set, but no scanned
items were indicated e.g. Intel ME files not specified.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/vendor.sh

@@ -486,6 +486,7 @@ patch_release_roms()
 		    "$vguide" > "$tmpromdir/README.md" || :
 	else
 		printf "Skipping vendorfiles on '%s'\n" "$archive" 1>&2
+		need_files="n"
 	fi
 
 	(