Bluetooth: Mgmt command for removing connection parameters

This patch introduces the MGMT_OP_REMOVE_CONN_PARAM which removes from
the controller's list the connection parameters from a given device.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Make find_conn_param() helper non-local

This patch makes the find_conn_param() helper non-local by adding the
hci_ prefix and declaring it in hci_core.h. This helper will be used
in hci_conn.c to get the connection parameters when establishing
connections.

Since hci_find_conn_param() returns a reference to the hci_conn_param
object, it was added a refcount to hci_conn_param to control its
lifetime. This way, we avoid bugs such as one thread deletes hci_conn_
param (e.g. thread running MGMT_OP_REMOVE_CONN_PARAM command) while
another thread holds a reference to that object (e.g thread carrying
out the connection establishment).	.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Use connection parameters if any

This patch changes hci_create_le_conn() so it uses the connection
parameters specified by the user. If no parameters were configured,
we use the default values.

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