drivers/intel/usb4: Add driver for USB4 retimer device

drivers/intel/usb4: Add driver for USB4 retimer device

The USB4 retimer device needs to declare a _DSM with specific functions
that allow for GPIO control to turn off the power when an external
device is not connected.  This driver allows the mainboard to provide
the GPIO that is connected to the power control.

BUG=b:156957424

Change-Id: Icfb85dc3c0885d828aba3855a66109043250ab86
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44918
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>