libertas: remove unused 11d code

Most of the 11d code was protected with an "if (priv->enable11d)" clause.
But there was no code that anywhere that was able to set this
variable to true. So all 11d code was dead for almost a year and no one
complained. That's enought incentive to remove this code.

Besides removing old cruft, we gain back the 11d capability in a common way
when we merge the cfg80211 functionality.

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>