advertising: Create and use scannable adv param flag

advertising: Create and use scannable adv param flag

In order for the advertising parameters hci request to indicate that an
advertising set uses a scannable PDU, we pass a scannable flag along
with the initial parameters MGMT request. This flag is populated based
on the existence of any scan response data requested by the client.

Without this patch, a broadcast advertisement with a scan response will
either be rejected by the controller, or will ignore the requested scan
response. The patch is tested by performing the above and confirming
that the scan response is retrievable from a peer as expected.

Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>