IB/rdmavt: Validate remote_addr during loopback atomic tests

IB/rdmavt: Validate remote_addr during loopback atomic tests

The rdma-core test suite sends an unaligned remote address and expects a
failure.

ERROR: test_atomic_non_aligned_addr (tests.test_atomic.AtomicTest)

The qib/hfi1 rc handling validates properly, but the test has the client
and server on the same system.

The loopback of these operations is a distinct code path.

Fix by syntaxing the proposed remote address in the loopback code path.

Fixes: 15703461533a ("IB/{hfi1, qib, rdmavt}: Move ruc_loopback to rdmavt")
Link: https://lore.kernel.org/r/1642584489-141005-1-git-send-email-mike.marciniszyn@cornelisnetworks.com
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>