Bluetooth: Add read_info management command

This patch implements the read_info command which is used to fetch basic
info about an adapter.

Signed-off-by: Johan Hedberg <johan.hedberg@nokia.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>