Always leave A/XBUS chiplets enabled
Always leave A/XBUS chiplets enabled

Since the XBUS chiplet contains logic required for other functions
(specifically PSI), we need to ensure that the HWPs are told the
chiplet is enabled.  The bus itself will be powered down at the IO
level so there are no power concerns.

Change-Id: I19ebf75c6377901937114bc6188d0793a3e78cd1
CQ: SW228043
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/6697
Tested-by: Jenkins Server
Reviewed-by: Andrew J. Geissler <c46de238cd554860f0bd4010b1729f1323facd9c@us.ibm.com>
Reviewed-by: MIKE J. JONES <3bfb5759ff83ad3ac713f701b283073623a8cdd2@us.ibm.com>
Reviewed-by: A. Patrick Williams III <c87e37b1a4035affd737b461af89fb722d635f4d@us.ibm.com>

csmart/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,csmart/hostboot,Over-enthusiastic/hostboot,csmart/hostboot,Over-enthusiastic/hostboot,alvintpwang/hostboot,alvintpwang/hostboot,open-power/hostboot,alvintpwang/hostboot,alvintpwang/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,alvintpwang/hostboot,csmart/hostboot,open-power/hostboot,Over-enthusiastic/hostboot,open-power/hostboot,csmart/hostboot