pds_vdpa: set features order

Fix up the order that the device and negotiated features
are checked to get a more reliable difference when things
get changed.

Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20231110221802.46841-4-shannon.nelson@amd.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>