Bluetooth: Add support for pairing via mgmt over LE

Using the advertising cache we are able to infer the type
of the remote device, and so trigger pairing over the correct
link type.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>