TODO
----

 - Decide upon main driver architecture.

 - Decide if the CG2900 driver should be a separate driver as today or if it
   should be a sub-driver using the TI-ST (Shared Transport) driver that is also
   written for a combo connectivity controller.

 - Decide if cg2900_uart should register on top of hci_ldisc.c (as now) or if it
   should instead register on top of hci_h4.c thereby reusing hci_h4
   implementation.

 - Update the hci_ldisc.c so that it will allow drivers to be registered without
   registering them directly to the Bluetooth stack. Also extend the hci_ldisc.c
   with more functions to abstract the tty API in a conformative way (currently
   sometimes the tty API used, sometimes the hci_ldisc interface).

 - Decide if the CG2900 driver should use imported structs and defines to create
   Bluetooth packets as today or if the Bluetooth stack in the Kernel should be
   extended so it is possible to use generic functions to send and receive
   commands and events both from the Bluetooth stack itself and from external
   drivers such as the CG2900 driver.