The old name "sysupgrade.sh" is easy to be confused with OpenWrt's
/sbin/sysupgrade. Rename our script to clearly indicate its
purpose.
While at it, move from /etc to /sbin, as the former is an odd location
for an executable script.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Fabian Bläse <fabian@blaese.de>