Currently for STA mode, depending on the scan_mode_6g ini value
driver will remove or add 6g channels to scan req, due to which
in some cases, scan is taking more time to complete.
Fix is to add new value to enum scan_mode_6g, when scan_mode_6g
ini value set to SCAN_MODE_6G_NO_OPERATION driver will not
modify the channel list.
Change-Id: I5b6891f142b54f4fa2fe6e9a75bf5fbd2e5f3adc
CRs-Fixed: 2783911