hw/rdma: Bugfix - Support non-aligned buffers

hw/rdma: Bugfix - Support non-aligned buffers

RDMA application can provide non-aligned buffers to be registered. In
such case the DMA address passed by driver is pointing to the beginning
of the physical address of the mapped page so we can't distinguish
between two addresses from the same page.

Fix it by keeping the offset of the virtual address in mr->virt.

Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Message-Id: <20180805153518.2983-13-yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>