Bluetooth: Refactor ioctl scan state update to its own function

Bluetooth: Refactor ioctl scan state update to its own function

With subsequent patches we'll also need to update the discoverable
state. As the code grows bigger it's better to move this out from the
switch statement into its own function.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>