Add rdimm decoder module, incorporate to base spd decoder

Change-Id: Id953cecfb0ed2b6d511b7652f917d618baa46a88
Original-Change-Id: I8137521ec1d2de48a389f769adda1068fe163376
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/28198
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Reviewed-by: JACOB L. HARVEY <jlharvey@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Brian R. Silver <bsilver@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/37399
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Tested-by: Daniel M. Crowell <dcrowell@us.ibm.com>