If user configures DFS channel in 160MHz mode,
1. change mode to 80MHz and do PreCAC on primary and
secondary channels of 160MHz.
2. Use intermediate channel to operate.
3. Once PreCAC done on the both primary and secondary channels and is clear
then change mode back to 160MHz.
4. Change the channel from intermediate to configured DFS channel.
Use Broadcast and Unicast OMN frame to notify mode change.
Change-Id: I451e35516ab4a44adea52a1342b5ea76d6e3d04f
CRs-fixed: 2395431
abbc0faf94