qcacld-3.0: Set OEM 6Ghz support only if Reg domain supports 6Ghz

Host uses "oem_6g_support_disable" INI value to configure
oem_6g_support_disable of wifi pos priv psoc object. If the Reg
domain doesn't support 6Ghz band and INI "oem_6g_support_disable"
value is 0, then host enables support for 6Ghz. Thus OEM apps
supporting 6Ghz fails to get 6Ghz channel information from host.
Hence use reg domain 6Ghz support  and "oem_6g_support_disable"
INI value to update oem_6g_support_disable of wifi pos priv psoc
object.

Change-Id: Id5e5b6220f3ce880da3c40aa959887ebc6bbfa7c
CRs-Fixed: 2870971