base-files: add reboot only button handler

For devices such as BTHOMEHUBV5A with both reset and restart buttons,
its easily accessible restart button has been assigned to KEY_POWER
power script to poweroff preventing accidental (or malicious) factory
resets by KEY_RESTART reset script. However an easily accessible button
immediately powering off the device is also undesirable.

Fixes: FS#1965
Signed-off-by: Alan Swanson <reiver@improbability.net>
Signed-off-by: Petr Štetiar <ynezz@true.cz> [long line wrap]

package/base-files/files/etc/rc.button/reboot

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+[ "${ACTION}" = "released" ] || exit 0
+
+if [ "$SEEN" -ge 5 ]
+then
+	echo "REBOOT" > /dev/console
+	sync
+	reboot
+fi
+
+return 0