usb: workaround non-working keyboards.

If the USB keyboard is not answering properly the first request on its
interrupt endpoint, just skip it and try the next one.

This workarounds an issue with a wireless mouse dongle which presents
itself both as a keyboard and a mouse but has a non-functional keyboard
interface.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
(cherry picked from commit 012bbf0ce0301be2482857e3f03b481dd15c2340)
Rebased to upstream/master:
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>