Bluetooth: Refactor SCO connection into its own function

We can do the same that we did for the other link types, for SCO
connections. The only thing that's worth noting is that as SCO
links need an ACL link, this functions uses the function that adds
an ACL link.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>