devices: virtio: vvu: allow non-zero guest mem descriptor offset
devices: virtio: vvu: allow non-zero guest mem descriptor offset

Fill the fd offset into the VmMemoryRequest::RegisterMemory source field
now that it is supported.

BUG=b:194136484
TEST=tools/presubmit

Change-Id: I9f8ae069d73cf0974bb739a768b731d6b0c289ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3508321
Reviewed-by: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm