Fix fapi getChildren for DIMMs

Found a swapped template parameter that made a check bad
Cleaned up some variable names to prevent similar errors

Change-Id: Ie86184a8d8842bfd42c9d022d05ed874f5c0ceda
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/41838
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>
Reviewed-by: Martin Gloff <mgloff@us.ibm.com>
Reviewed-by: Christian R. Geddes <crgeddes@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>