Bluetooth: btusb: Add option for Broadcom protocol support

With the generic Broadcom Bluetooth support module, it is possible to
turn support for firmware and patchram download into an optional
feature.

To keep backwards compatibility with previous kernel configurations,
the new option defaults to enabled.

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