qcacld-3.0: Check band caps before initializing wiphy band

Currently driver initializes the wiphy 6ghz band without
checking the band capability. If FW does not support 6Ghz
then wiphy register is failed as wiphy 6ghz band is initialized
by driver.

To fix this, initialize the wiphy 6ghz band only when host
driver and FW both supports 6Ghz band.

CRs-Fixed: 2968968
Change-Id: I28d660f515d16d0eb4245311b42c69308576ac62