Try to match PRI/SEC channel with neighboring 20/40 MHz BSSes per
IEEE 802.11n/D7.0 11.14.3.2. This is not yet complete implementation,
but at least some parts of the 40 MHz coex are improved.
40 MHz operation maybe rejected (i.e., fall back to using 20 MHz) or
pri/sec channels may be switched if needed.
driver.h contains the definitions needed in driver wrapper
implementations (driver_*.c) and driver_i.h contains the definitions
that are used in core hostapd code to interact with the driver wrappers.