* bus/usb/ohci.c (grub_ohci_pci_iter): Define the Class,
Subclass and Programming Interface fields in terms of the 3 byte
Class Code register.
* bus/usb/uhci.c (grub_uhci_pci_iter): Likewise.
* bus/usb/ohci.c (grub_ohci_pci_iter): Check that programming
interface is OHCI. Add grub_dprintf for symmetry with
bus/usb/uhci.c.
* bus/usb/uhci.c (grub_uhci_pci_iter): Check that programming
interface is UHCI. Add interf variable for programming
interface. Print interface with class/subclass.