Bluetooth: btintel: Refactoring setup routine for legacy ROM sku

This patch refactors the setup routines for legacy ROM product into
combined setup, and move the related functions from btusb to btintel.

Signed-off-by: Tedd Ho-Jeong An <tedd.an@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>