hostapd: Check for overlapping 20 MHz BSS before starting 20/40 MHz BSS

hostapd: Check for overlapping 20 MHz BSS before starting 20/40 MHz BSS

Before starting a 20/40 MHz BSS on the 2.4 GHz band, a 40-MHz-capable HT
AP is required by the rules defined in IEEE Std 802.11-2012 10.15.5 to
examine the channels of the current operational regulatory domain to
determine whether the operation of a 20/40 MHz BSS might unfairly
interfere with the operation of existing 20 MHz BSSs. The AP (or some of
its associated HT STAs) is required to scan all of the channels of the
current regulatory domain in order to ascertain the operating channels
of any existing 20 MHz BSSs and 20/40 MHz BSSs. (IEEE 802.11-2012 S.5.2
Establishing a 20/40 MHz BSS).

Add the check for an overlapping 20 MHz BSS to the initial AP scan for
the P == OT_i case in 10.15.3.2.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>