RPi4's firmware doesn't support receiving two USB reset signals in a row, even
though it's supposed to do so (funnily enough 3 resets in a row work fine).
This leaves the xHC in a broken state for TW as both u-boot and Linux perform
this operation.

I'm in contact with the RPi engineers and a firmware fix should show up
eventually. That said we're in the middle of the holiday season, so we'll have
to be patient. We could advise TW users to kexec into the same Linux image to
trigger a third USB reset, which will fix the issue, but that seems overkill.
Otherwise, I prepared a small kernel fix to bypass the reset signal if USB is
already up. This fix will never make it upstream, as it's somewhat hacky. But I
figure it'll be nice to port it to TW while we wait for the RPi foundation to
publish a new firmware.