[coreboot] EHCI debug port finder

[Carl-Daniel Hailfinger]

I wanted to know which physical port of my multiple USB controllers have
the debug capability. There was no way to find that easily, so I created
a tool which will do most of the work for the user.

Example output:
The following PCI devices support a USB debug port (says lspci):
0000:00:1d.7
The following PCI devices support a USB debug port (says the kernel):
0000:00:1d.7
PCI device 0000:00:1d.7, USB bus 3, USB physical port 1
Currently connected high-speed devices:
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/6p, 480M
    |__ Port 2: Dev 20, If 0, Class=stor., Driver=usb-storage, 480M

The output can be improved, but it's a good start.

Regards,
Carl-Daniel