qcacmn: Do not allow to set same 6G AP power mode
The API that takes in the input 6G AP power type and updates current
channel list, allows setting the same power type which is not needed and
is a costly operation.
Change-Id: Ia690f40a6796a0db243f0abd15f2eebc8340d1d9
CRs-Fixed: 3051502