vhost-vdpa: fix vhost_vdpa_map() on error condition

vhost-vdpa: fix vhost_vdpa_map() on error condition

[ Upstream commit 1477c8aebb94a1db398c12d929a9d27bbd678d8c ]

vhost_vdpa_map() should remove the iotlb entry just added
if the corresponding mapping fails to set up properly.

Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Link: https://lore.kernel.org/r/1601701330-16837-2-git-send-email-si-wei.liu@oracle.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>