netcardconfig: drop uncommon wireless/WiFi options

No longer ask for the following options WiFi:

* iwconfig
* iwpriv
* iwspy
* wireless-channel
* wireless-freq
* wireless-nwid
* wireless-mode

AFAICT it's unusual to set those options to something other than the
defaults, at least nowadays. So let's drop support for it, minimizing
questions to answer in interactive mode (which also minimizes porting
efforts if we ever rewrite netcardconfig, see
https://github.com/grml/grml-network/issues/11).

FTR: according to my tests, wireless-tools seems to do the right™ thing
by default regarding "wireless-mode".