Fixed ipl mk file to include unmasking code

Change-Id: Ic1518e127e9b58f669d78cbdd8b0a337986d20f5
Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/96663
Reviewed-by: Christian R Geddes <crgeddes@us.ibm.com>
Reviewed-by: Caleb N Palmer <cnpalmer@us.ibm.com>
Reviewed-by: Zane C Shelley <zshelle@us.ibm.com>
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com>
Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com>
Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com>
Reviewed-by: Daniel M Crowell <dcrowell@us.ibm.com>

src/usr/diag/prdf/prdf_hb_only.mk

@@ -281,6 +281,7 @@ prd_obj_no_sim += adr32s_workarounds.o
 prd_obj_no_sim += dcd.o
 prd_obj_no_sim += rdimm_raw_cards.o
 prd_obj_no_sim += lrdimm_raw_cards.o
+prd_obj_no_sim += exp_unmask.o
 
 ################################################################################
 # The following are hardware procedure utilities that we are pulling into the