Bluetooth: Remove unused btuart_cs driver

With patch 279c9361 the btuart_cs driver has been deprecated in
favor of serial_cs + hci_uart combination.

  static struct pcmcia_device_id btuart_ids[] = {
         /* don't use this driver. Use serial_cs + hci_uart instead */
         PCMCIA_DEVICE_NULL
  };

Intead of keeping it around, just remove it since it is not even
assigned to any PCMCIA identifiers anymore.

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