I've just consolidated the several variants of usbehci.c into port/usbehci.c, and moved usb.h into port. There is now port-specific ehci initialisation and shutdown code in files with names like usbehcipc.c. mkfiles and kernel configuration files have had to be changed; the configuration line for ehci is now something like
usbehci usbehcipc I think I've made the necessary changes to files on sources. After pulling these changes, you should probably `cd /sys/src/9; mk clean' before building any new kernels.