Translate offsets to destination address space

Translate offsets to destination address space

The 'offset' field in RDMACompress and 'current_addr' field
in RDMARegister are commented as being offsets within a particular
RAMBlock, however they appear to actually be offsets within the
ram_addr_t space.

The code currently assumes that the offsets on the source/destination
match, this change removes the need for the assumption for these
structures by translating the addresses into the ram_addr_t space of
the destination host.

Note: An alternative would be to change the fields to actually
take the data they're commented for; this would potentially be
simpler but would break stream compatibility for those cases
that currently work.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>