[coreboot] [PATCH]Changes to libpayload's USB stack

[Patrick Georgi]

Hi,

attached patch
- avoids using the name "pid_t", which is used on unixoid systems
- moves controller specific data structures into private headers,
  to avoid conflicts between controller drivers
- factors out the USB PID ids, which are only exposed on UHCI. It's
  of not much use on the other controllers.

It requires a copy of uhci.h to uhci_private.h

Signed-off-by: Patrick Georgi