libertas: remove lots of unused stuff

This removes many unused function parameters as well as some not-implemented
functions, e.g. CMD_802_11_GET_STATS. The silly lbs_set_cmd_ctrl_node()
function is now also gone.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>