This commit merges the driver_ops structures and implementations from
hostapd/driver*.[ch] into src/drivers. This is only an initial step and
there is room for number of cleanups to share code between the hostapd
and wpa_supplicant parts of the wrappers to avoid unnecessary source
code duplication.
This uses similar, but not identical, interface to madwifi. It is easier
to keep this separate to avoid conflicts with potential changes in the
driver interfaces.