Bluetooth: Discovery parameters per hci_dev

This patch adds discovery parameters to struct hci_dev. This way, we
will be able to configure the discovery parameters per hci device.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Export discovery parameters to debugfs

This patch exports discovery parameters under hciX directory/. All
parameter files have read and write permissions. This means, we
are able to change discovery parameters by writing new values into
the files. For instance, to change the default value for the scanning
interval we can run:
$ echo 0x0016 > /sys/kernel/debug/bluetooth/hci0/discov_scan_interval

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>