dpp-nfc: Do not hardcode netrole for NFC Tag writing cases

dpp-nfc: Do not hardcode netrole for NFC Tag writing cases

Allow netrole to be specified for NFC Tag writing cases. Previously,
this was hardcoded to use netrole=configurator when starting the listen
operation. Now the netrole parameter is not included by default, but any
netrole value can be specified with the new --netrole command line
argument.

In addition, fix the listening frequency for the case where a channel is
picked.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>