Some multi-function input devices (e.g. combo keyboard and mouse)
present as IAD-style devices (https://www.usb.org/defined-class-codes,
https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-interface-association-descriptor).
Historically, multi-function devices would report a DeviceClass of 0,
indicating that interface matching should be done on the interface
descriptor rather than the global device descriptor.
IAD-style devices us DeviceClass of 0xEF, so they don't match
MatchUsbClass() for keyboard (DeviceClass=3, SubClass=1, Proto=1). If
they are treated as if they had a DeviceClass of zero, which is more
traditional for legacy multi-function devices, then the interface
descriptors are used instead and these types of devices will "just work"
without needing to add a custom USB device path to ConIn.
Signed-off-by: Aaron Pop <aaronpop@microsoft.com>
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