kernel: Remove random_poll().

It is no longer used since device polling was torn out in favor of
kq filters in 163625b9bf04f32ec3cbbaef7e6b242aeb8a152c.
kernel - Fix bug in ehci port reset code

* Fix a bug when the port reset fails where the port locks up and no longer
  works.  The reset code was returning without disposing of the transfer
  request.

* Some devices (usually smart phones) won't reset on the first attempt.
  Try at least twice before reporting an error.

* Change the PR clear test to wait up to one second, instead of 250ms.