New: Simplefirewall

Re-add missing function

RMxxx_rgmii_toolkit.sh

@@ -107,6 +107,10 @@ is_simple_firewall_installed() {
     fi
 }
 
+# Check if Simple Admin is installed
+is_simple_admin_installed() {
+    [ -d "$SIMPLE_ADMIN_DIR" ] && return 0 || return 1
+
 # Function to install/update Simple Firewall
 install_update_simple_firewall() {
     echo "Installing/Updating Simple Firewall..."