usbdebug: Split PCI EHCI part

There are EHCI compatible host controllers on ARM without PCI bus
architecture. Currently we have not come across one with the debug
capability though.

Change-Id: I8775c9814f6fdf8754f97265118a7186369d721d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5175
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/include/device/pci_def.h

@@ -181,6 +181,7 @@
 #define  PCI_CAP_ID_CHSWP	0x06	/* CompactPCI HotSwap */
 #define  PCI_CAP_ID_PCIX	0x07	/* PCIX  */
 #define  PCI_CAP_ID_HT          0x08	/* Hypertransport */
+#define  PCI_CAP_ID_EHCI_DEBUG	0x0A	/* EHCI debug port */
 #define  PCI_CAP_ID_SHPC 	0x0C	/* PCI Standard Hot-Plug Controller */
 #define  PCI_CAP_ID_PCIE	0x10	/* PCI Express */
 #define  PCI_CAP_ID_MSIX	0x11	/* MSI-X */