Currently the IDDRs are configured in SAME_EDGE_PIPELINED mode, but then
the negative data is delayed by an additional clock cycle. This is the same
behaviour as using the IDDR in SAME_EDGE mode.
Switching to SAME_EDGE mode removes extra pipelining registers while
maintaining the same behaviour.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>