Bluetooth: btbcm: Add helper functions for UART setup

Firmware loading may reset the controller UART speed and needs to set
host UART speed back to init speed.

UART drivers setup is split in 3 parts:
- btbcm_initialize() resets the controller and returns the firmware
  name based on controller revision and sub_version.
- btbtcm_patchram() (already existing and public), which takes the
  firmware name as parameter, requests the firmware and loads it to
  the controller.
- btbcm_finalize() which resets the controller, reads local version
  and checks if the controller address is a default one or not.

Remove firmware name retrieval for UART controllers from
btbcm_setup_patchram().

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>