AccessLevel: fix method toString()
AccessLevel: fix method toString()

The conversion of NONE is wrong as NONE is the highest value.

Fixes: c733769bd587 ("AccessLevel: new class")
Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server