Add socat apt package for kshell

Fixes: 294300493

Change-Id: If5ddb938305c9dadd0193ed844d6b324b8a7b7d2

install-prereqs.sh

diff --git a/install-prereqs.sh b/install-prereqs.sh
index 5dae9f7..57a896d 100755
--- a/install-prereqs.sh
+++ b/install-prereqs.sh
@@ -85,6 +85,7 @@
     python3-pip
     python3-venv
     rsync
+    socat
     srecord
     texinfo
     texlive-bibtex-extra