Bluetooth: Remove min/max connection interval from hci_conn

hci_conn already keeps track of connection parameters so there is
no reason to save minimum and maximum connection interval values in
hci_conn. Therefore, this patch removes them.

Since they are removed from hci_conn, this patch also moves the
connection parameters lookup to hci_req_add_le_create_conn().

The minimum and maximum connection interval values are reported
to user through a mgmt event. This event is sent during Connection
Parameter Update Procedure.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Export slave latency parameter

This patch exports slave latency parameter through Bluetooth debugfs
interface. The default value is 0 and it may be changed by writing the
new value in conn_latenty file. The acceptable values range from 0x0000
to 0x01F3, according described in Core 4.1, Vol 2, 7.8.12.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Export supervision timeout parameter

This patch exports supervision timeout parameter through Bluetooth
debugfs interface. The default value is 0x002a and it may be changed by
writing the new value in conn_supervision_timeout file. The acceptable
values range from 0x000a to 0x0c80 according described in Core 4.1,
Vol 2, 7.8.12.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Extend LE connection parameters infrastructure

This patch extends connection parameters infrastructure (hci_conn_
params and helper functions) to consider slave latency and supervision
timeout parameters.

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