Bluetooth: LE Set Scan Parameter Command

This patch adds the parameter struct and the command complete event
handler to the LE Set Scan Parameter HCI command.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>