pru: Update installation and flash scripts

Update the scripts used to install and "flash" the pru
micro-controller code.  Also, add a "flash" script for the linux
micro-controller code.  This makes it easier to install Klipper on a
Beaglebone board that uses a Replicape.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

scripts/flash-linux.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# This script installs the Linux MCU code to /usr/local/bin/
+
+if [ "$EUID" -ne 0 ]; then
+    echo "This script must be run as root"
+    exit -1
+fi
+set -e
+
+# Install new micro-controller code
+echo "Installing mirco-controller code to /usr/local/bin/"
+rm -f /usr/local/bin/klipper_mcu
+cp out/klipper.elf /usr/local/bin/klipper_mcu
+sync
+
+# Restart (if system install script present)
+if [ -f /etc/init.d/klipper_pru ]; then
+    echo "Attempting host MCU restart..."
+    service klipper_pru restart
+fi