CSPLITs for INTERRUPT transactions have to be scheduled in each microframe
following the SSPLIT. INTERRUPT transfers are executed in the next even/
odd microframe depending on the HCCHAR_ODDFRM flag.

As there are no handshakes for INTERRUPT SSPLITs the SSPLIT may have
failed (transport error) without the error being detected by the host
driver. If the last CSPLIT is not received within 4 microframes after the
SSPLIT there was a transaction error and the complete transaction has
to be restarted.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>