vfio: move implement of vfio_get_xlat_addr() to memory.c

vfio: move implement of vfio_get_xlat_addr() to memory.c

- Move the implement vfio_get_xlat_addr to softmmu/memory.c, and
  change the name to memory_get_xlat_addr(). So we can use this
  function on other devices, such as vDPA device.
- Add a new function vfio_get_xlat_addr in vfio/common.c, and it will check
  whether the memory is backed by a discard manager. then device can
  have its own warning.

Signed-off-by: Cindy Lu <lulu@redhat.com>
Message-Id: <20221031031020.1405111-2-lulu@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>