rdma: introduce qemu_update_position()

rdma: introduce qemu_update_position()

RDMA writes happen asynchronously, and thus the performance accounting
also needs to be able to occur asynchronously. This allows anybody
to call into savevm.c to update both f->pos as well as into arch_init.c
to update the acct_info structure with up-to-date values when
the RDMA transfer actually completes.

Reviewed-by: Juan Quintela <[email protected]>
Tested-by: Chegu Vinod <[email protected]>
Tested-by: Michael R. Hines <[email protected]>
Signed-off-by: Michael R. Hines <[email protected]>
Signed-off-by: Juan Quintela <[email protected]>