This needs to find the PRI channel also in cases where the affected
channel is the SEC channel of a 40 MHz BSS, so need to include the
scanning coverage here to be 40 MHz from the center frequency. Without
this, it was possible to miss a neighboring 40 MHz BSS that was at the
other end of the 2.4 GHz band and had its PRI channel further away from
the local BSS.
Signed-off-by: Jouni Malinen <j@w1.fi>