fff-hoods: move hiddenapfile variable

Move the variable definition to the implementation file. This is more
intuitive and the variable is not used otherwise.

Signed-off-by: Tim Niemeyer <tim@tn-x.org>
Reviewed-by: Christian Dresel <fff@chrisi01.de>
Reviewed-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>