tools: add tools/spl_size_limit to ignore list

This tool has just been added but it seems I forgot to add it to
the ignore list. So to prevent the built binary being marked as
unversioned, add it to the ignore list.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
diff --git a/tools/.gitignore b/tools/.gitignore
index e5ede22..767b056 100644
--- a/tools/.gitignore
+++ b/tools/.gitignore
@@ -27,6 +27,7 @@
 /prelink-riscv
 /proftool
 /relocate-rela
+/spl_size_limit
 /sunxi-spl-image-builder
 /ubsha1
 /xway-swap-bytes