nl80211: Add support for minimal probe request content

nl80211: Add support for minimal probe request content

Extend 'struct wpa_driver_scan_params' to allow higher layer to indicate
if minimal probe request content should be included by the driver as part
of the scan logic.

Implement this with driver_nl80211, by setting
NL80211_SCAN_FLAG_MIN_PREQ_CONTENT.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>