Bluetooth: btbcm: Consolidate the controller information commands

The commands that read the basic vendor information about the Broadcom
controller are duplicated for UART and USB devices. Combine them into a
single function to reduce the code complexity.

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