Bluetooth: Refactor LE connection into its own function

The code that handles LE connection is already quite separated from
the rest of the connection procedure, so we can easily put it into
its own.

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