Bluetooth: Allow L2CAP getpeername() for BT_CONFIG state

We have all the necessary remote information for getpeername() when we
are in the BT_CONFIG state so this should be allowed. This is
particularly important for LE sockets where changing the security level
will temporarily move the socket into BT_CONFIG state.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>