mac80211: add PID controller based rate control algorithm
Add a new rate control algorithm based on a PID controller. It samples the
percentage of failed frames over time, feeds the result into the controller and
uses its output to control the TX rate.
Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>