spapr: Abolish DRC get_fdt method

spapr: Abolish DRC get_fdt method

The DRConnectorClass includes a get_fdt method.  However
  * There's only one implementation, and there's only likely to ever be one
  * Both callers are local to spapr_drc
  * Each caller only uses one half of the actual implementation

So abolish get_fdt() entirely, and just open-code what we need.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Daniel Barboza <danielhb@linux.vnet.ibm.com>