wil6210: add support for discovery mode during scan

Add support for discovery mode during scan. When discovery mode
is active, station transmits special beacons while scanning.
This can optimize the scan mainly when there is only one AP/PCP
around.
Discovery mode is implicitly used by firmware during P2P search.
Since there is currently no use case where user space has a
reason to directly control discovery mode, we expose it only
through a debugfs flag.
Also fix name confusion in the wmi_scan_type enumeration.
The type previously called WMI_LONG_SCAN is actually
WMI_ACTIVE_SCAN.

Change-Id: I05b99ec66b0da41697f41c547aab0b0497dd9be6
Signed-off-by: Lior David <qca_liord@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
Git-commit: 74997a53d257e327699e359b78b3ecfd33f80cab
Git-repo: https://github.com/kvalo/ath.git


CRs-Fixed: 982931
Signed-off-by: Maya Erez <merez@codeaurora.org>