device: Move pnp_device allocator down from ram to romstage

...TODO

  /\_/\
=( °w° )=
  )   (  //
 (__ __)//

Change-Id: Ia0de681537975ec1c66806302a61c24074100198
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>