Add base spd decoder to share among controllers

Reorganized files and names to make room for
DDR3 SPD decoder to be used for Cumulus.

Change-Id: I63cdc30fb50041e07e09ddfe8301159ecd2bedae
Original-Change-Id: Id3e7a8f4bb60fd0ae0cdf36b8298a1d00257205a
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/36319
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Brian R. Silver <bsilver@us.ibm.com>
Reviewed-by: STEPHEN GLANCY <sglancy@us.ibm.com>
Reviewed-by: Louis Stermole <stermole@us.ibm.com>
Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/54755
CI-Ready: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Tested-by: Daniel M. Crowell <dcrowell@us.ibm.com>