The sync_data module can be used to continuously transfer multi-bit signals
like status signals safely from the source to the destination clock
domain. A transfer takes 2 source and 2 destination clock cycles. It is not
guaranteed that all transitions on the source side will be visible on the
target side if the signal is changing faster than this. Logic using this
block should be aware of it. The primary intention is for it to be used for
slowly changing status signals.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>