pds_vdpa: fix up debugfs feature bit printing

Make clearer in debugfs output the difference between the hw
feature bits, the features supported through the driver, and
the features that have been negotiated.

Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20230711042437.69381-6-shannon.nelson@amd.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>