Channel switching issue in AP mode

[darkdarkgray]

https://github.com/qca/sigma-dut/blob/d2b559b7d33cde0a3b2eec32f6482e568a8968fe/ap.c#L12855
Hostapd failed when we try to switch channel with sigma_dut in AP mode and bandwidth 80MHz and more.
Because of hardcoded "sec_channel_offset=1" we can switch only to half of channels list. (36 - ok, 40 - failed, 44 - ok, 48 - failed, etc).
To fix that we need to calculate sec_channel_offset according to channel frequency, center_freq1 and bandwidth.