Implemented rate adaptation support via 'iwconfig rate' API.  It is now
possible to specify a bit-rate value and append 'auto'.  That will configure
rate adaptation to use all bit-rates equal or lower than than selected value.

Made lbs_cmd_802_11_rate_adapt_rateset a direct command.
Signed-off-by: NJavier Cardona <javier@cozybit.com>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
Acked-by: NDan Williams <dcbw@redhat.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>