mb/google/rex: Mark unused USB ports as empty

This patch marks unused USB ports (USB2.0/TCSS) empty to avoid
prompting wrong dmesg as below.

   ```
  usb usb2-port3: Cannot enable. Maybe the USB cable is bad?
   ```
Mainboard variants to override the USB ports as per the target
board design.

TEST=Able to build and boot google/rex with all USB ports are
working as expected.

Change-Id: Ic3d21151a22f2318413f480f3386bf2dbf696307
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73027
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

0 files changed, 0 insertions, 0 deletions