[coreboot] [PATCH]Move USB debug port includes out of romstage

[Patrick Georgi]

Hi,

attached patch does:
- move EHCI_BAR_INDEX to ehci.h - it's constant as per EHCI spec 2.3.1
- move EHCI_BAR and EHCI_DEBUG_OFFSET to Kconfig to be set by USB debug
port enabled southbridges
- drop USB debug code includes from romstage.cs and use romstage-srcs in
the build system instead
- Disable USBDEBUG in abuild, I forgot this by accident before the
previous commit

It's abuild tested.

Signed-off-by: Patrick Georgi