libertas: remove Beacon Control

For now; it's a pretty easy command to hook up and whenever OLPC
figures out how they want the userspace interface to look (ie,
not iwpriv commands) we can easily add it back in.  Since the
cfg80211 conversion it wasn't working anyway.

Signed-off-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>