Treat WEP like WPA: only offer if supported

Treat WEP like WPA:  only offer if supported

WEP does not work with our bwfm(4) and it shows:
    Which network interface do you wish to configure? (or 'done') [bse0] bwfm0
    ifconfig: SIOCS80211NWKEY: Operation not supported by device
    Access point? (ESSID, 'any', list# or '?') [any] 2
    Security protocol? (O)pen, (W)EP, WPA-(P)SK [O]

Handle the error and disable (W)EP unless the driver has it.

No objections from anyone.