qcacld-3.0: Add support to get roam scan frequencies

For user request of get roam scan frequencies using vendor sub command
QCA_WLAN_VENDOR_ROAMING_SUBCMD_CONTROL_GET and vendor sub attribute
QCA_WLAN_VENDOR_ATTR_ROAMING_PARAM_CONTROL, host replies with list
of roam scan frequencies.

Change-Id: Ia63a5181e13541629a380dec9a032743d15add0c
CRs-Fixed: 2725834
3 files changed