Diff reduction to NetBSD.
Diff reduction to NetBSD.

MFNetBSD 1.177; author: toshii
   Use the correct wValue to get hub desriptors.
   Also, make wValue checks of root hub codes less strict.

MFNetBSD 1.178: author: martin
   Interrupt descriptors might become invalid while being processed in
   uhci_check_intr - so remember their next pointer before calling it.
   Patch provided by Matthew Orgass in PR kern/24542.

Obtained from:   NetBSD

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