This PR adds the ability to choose which companion controller the EHCI
uses.
`#usb_ehci: enabled=1, companion=uhci`
`#usb_ehci: enabled=1, companion=ohci`
UHCI is enabled by default:
`#usb_ehci: enabled=1`
This breaks up `usb_ohci.cc/h` into `usb_ohci.cc/h` and `ohci_core.cc/h`
to be like the existing `usb_uhci.cc/h` and `uhci_core.cc/h`.
This adds the ability to define a Port Routing string in the
`HcspPortRoute` register, and is optional via the `EHCI_PORT_ROUTE`
define.
Currently `EHCI_N_CC` and `EHCI_N_PCC` must remain as currently set (3
and 2 respectively), however with a little more work, I think these can
be modified and have up to 7 companion controllers with more ports per
companion, as long as the combined total is <= 15 total ports.
Please verify the `Makefile.in` changes. I do not use GCC and can not
verify it is correct.
