Onboard USB controller passthrough

[Peter Grehan]

>> The controllers looks like this
>>
>> # pciconf -l -BbcV ppt2 at pci0:0:26:0
>> ppt2 at pci0:0:26:0:       class=0x0c0320 card=0x72708086 chip=0x8d2d8086
>> rev=0x05 hdr=0x00
>>      bar   [10] = type Memory, range 32, base 0xc6134000, size 1024, enabled
>                                                             ^^^^^^^^^^^^
> 
>>      cap 01[50] = powerspec 2  supports D0 D3  current D0
>>      cap 0a[58] = EHCI Debug Port at offset 0xa0 in map 0x14
>>      cap 13[98] = PCI Advanced Features: FLR TP

  More importantly, EHCI controllers don't support MSI/MSI-x interrupts 
which is currently required for bhyve PCI-passthru.

later,

Peter.