This replaces deprecated backticks by more versatile $(...) syntax.
This does not touch lib/upgrade/nand.sh, as there replacement is
not trivial.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
This may be useful if you don't entirely trust your flash and want to be able
to check for corruptions.
Signed-off-by: Michal Hrusecky <Michal@Hrusecky.net>