Allow SCAN command to specify scan_ssid=1 SSIDs

Allow SCAN command to specify scan_ssid=1 SSIDs

The new "scan_id=<comma separated list of network ids>" parameter can
now be used to specify a list of network ids that have scan_ssid=1 to
indicate active scanning of the SSID. This adds the listed SSIDs to the
scan command to allow manual scan requests to perform active scans for
hidden SSIDs. For example, "SCAN scan_id=1,7,11" would run a scan with
the SSID fetched from the configured network blocks 1, 7, and 11
(assuming those are set with scan_ssid=1). The SSIDs will be included
even from network blocks that are currently disabled.

The maximum number of SSIDs added to the request is limited by the
driver support. If more than supported values are specified, the command
will fail (returns "FAIL").

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>